The movement at large strikes me as too prestige-seeking and power-seeking, and as such has pretty strong antibodies against a lot of stuff that could potentially, hypothetically, pose a PR risk or make enemies of any kind, or seem generally off-putting to anyone. 

I have found that when I identified as an EA, I had a lot more unproductive critical voices in my head that prevented me from considering a lot of potentially good ideas, and it exposed me to a lot of people who would get angry at me if I did anything that "damaged the reputation of the movement". After many years of actively carrying EA as part of my identity, I had noticed that my ability to take directed action in the world had very greatly atrophied, I was much more anxious and risk-averse, and it took me at least two years of internally distancing myself quite a lot from the EA-identity cluster before I felt like I could have novel ideas again and start working on ambitious projects again. 

In short, overall identifying as an EA and placing myself as a representative of the EA community made me much worse at thinking and achieving difficult things. These days I am holding the identity very much at a distance, but am of course still active in the community. I still find this pretty stressful, but mostly think the costs are worth it.

I'm bothered by a certain type of way I observe a significant number of EAs orienting toward the non-EA world. To me, it feels like there can be a lack of understanding, appreciation, and respect for the work/thoughts/opinions/accomplishments/culture of non-EAs that I sometimes find particularly naive and alienating. These experiences in particular drive me to have hesitance in self-identifying  as an EA.

I don't feel comfortable saying 'I'm an effective altruist', though if someone asks me if I am one the most truthful answer is clearly 'yes'. I think I'm not that keen on labels in general, though there are some I'm comfortable with, including 'feminist' and 'utilitarian'.  I was one of the participants Jonas mentions. 

This is basically an instinct rather than a thought-through opinion, but at a guess, the biggest reasons for my hesitation are: 
- It feels self-aggrandising to call myself 'an effective altruist'. It feels hard to really know that I'm altruistic (as opposed to doing work I find fulfilling for example), and even harder to know that insofar as I'm altruistic, I'm being effective about it. On the other hand, I understand utilitarian to mean something like 'I think better outcomes are the ones with more wellbeing in, and those are the ones I'm aiming at'. That feels like something I'm happy to claim. 
- Identifying some people as 'effective altruists' feels like it's dividing people unnecessarily. I think most people want to help others, and most people would like to do so in a way that's effective rather than ineffective. Obviously, I really like the idea of there being tools and mechanisms (like this forum) for helping people do that, and also a community of people trying particularly hard to do this and do so in particular ways. And having some label for those does seem useful, so it does seem hard not to do this 'identifying'.  

For me, I don't think there is a single dominant reason. Some factors that seem relevant are:

• Moral uncertainty, both at the object-level and regarding metaethics, which makes me uncertain about how altruistic I should be. Forming a community around "let's all be altruists" seems like an epistemic error to me, even though I am interested in figuring out how to do good in the world.
• On a personal level, not having any close friends who identify as an effective altruist. It feels natural and good to me that a community of people interested in the same things will also tend to develop close personal bonds. The fact that I haven't been able to do this with anyone in the EA community (despite having done so with people outside the community) is an indication that EA isn't "my people".
• Insufficiently high number of people who I feel truly "get it" or who are actually thinking. I think of most people in the movement as followers or promoters and not even doing an especially good job at it.
• Generic dislike of labels and having identities. This doesn't explain everything though, because I feel less repulsed by some labels (e.g. I feel less upset about calling myself a "rationalist" than about calling myself an "effective altruist").

I see "effective altruist" as a dodgy shorthand for the full term: "aspiring effective altruist". I'm happy to identify as the latter in writing (though it is too clunky for speech).

I'm a big fan of EA philosophy and the people I've met through EA. But I think of EA as a philosophy/movement/personal practice, not a political party or a religion or any other thing that naturally seems to grant an "-ist" label.

While I'm sure I sometimes lapse into the "EAs" shorthand in conversation/casual commenting, I try to avoid it in everything I write for CEA, and I push (gently) to keep it out of things I edit/review for others.

My preference is to say "I try to practice effective altruism" or "I try to follow the principles of effective altruism" (more precise, but clunkier). There are things I associate with EA (trying to increase impact, being cause-neutral, weighting different sorts of beings equally, considering counterfactuals) that I try to do, but don't always succeed at. That's what defines an "EA" to me — goals and behaviors.

I don't think I've ever called myself an effective altruist, part of it is the small identity idea mentioned in the original post and another part is that it doesn't seem correct to call myself effective when there are large uncertainties about the prioritisation of causes and interventions, so new evidence could come up showing I was actually very ineffective.

On a more practical level, it's easier to have conversations with people who are newer to EA or are sceptical of certain aspects of it when I'm not calling myself an EA and making it seem like something you are either in or out of.

It's also probably easier to find flaws in a topic when it isn't part of your identity, it reduces the chance of defensiveness, and I think I should try and make it easy to always be open to potential problems in EA.

I feel fine about referring to myself as "an EA" in contexts where this is convenient and doesn't imply major "identity" or "ideological" commitments. And indeed I sometimes do so.

In many ways the label does seem quite descriptive of my views and career goals.

I don't feel like I identify as an EA in any strong sense, or like I would want to describe myself as such no matter the context. For me, this partly has to do how I think about EA relative to other life goals. The way I roughly see it now, maximizing impartial goodness is one of the most important goals I'm pursuing; but there are also other, more personal goals. I feel like tying my identity to just one of them would "privilege" that one goal at the expense of others, in a way that messes with my way of internally resolving conflict between them (and of course such conflicts sometimes to come up). This feels true to me even if it turned out that in some sense, maximizing impartial goodness was my most important goal, or the one I cared most about, or similar.

For a couple of months during the first year after I had encountered EA I was more in a mindset of "EA is the most important/only goal, and I can pursue other goals only insofar as they're instrumentally useful or it would be psychologically impossible for me to not pursue them". Partly this was due to bad social influences. This isn't exactly the same as "identifying as an EA", but I now think my mindset at the time was both unhealthy and instrumentally harmful for my long-term ability to do good, and so it's one key reason for why I'm skeptical about, in some sense, "emphasizing EA too much".

[I wasn't at the Leaders Forum 2019.]

My reservation is around the idea of keeping my identity small, as Jonas suggested in his post. I feel 5/5 as a member of the EA community,  I’m just worried prominently giving myself tags like „I am an Effective Altruist“, or „Feminist“, “German“, „Man“, “Vegan“ etc. comes with baggage that will constrain my thinking and behavior without many benefits, compared to saying „I am part of the EA community, I come from Germany, my diet is vegan, I care about XYZ“.

I'll note that I used to have some reservations but no longer do, so I'll answer about why I previously had reservations.

When EA got interested in what we now call longtermism, it didn't seem obvious to me that EA was for me. My read was that EA was about near concerns like global poverty and animal welfare and not far concerns like x-risk and aging. So it seemed natural to me that I was on the outside of EA looking in because my primary cause area (though note that I wouldn't have thought of it that way at the time) wasn't clearly under the EA umbrella.

Obviously this has changed now, but hopefully useful for historical purposes, and there may be folks who still feel this way about other causes, like effective governance, that are, from my perspective, on the fringes of what EA is focused on.

Even though I identify strongly with the EA movement, I want to be humble about how much my actions actually benefit the world, especially when I have so little experience and wisdom. So I tend to identify as an "aspiring EA" or "adherent of EA."

Reasons not to identify as EA to me are just nuances about identities altogether and trying to keep them small (http://www.paulgraham.com/identity.html). 

1. Social group membership is not upstream. "trying to believe true things" or "trying to win" are the things I aspire to upstream, and maybe some social groups, like EA, are instrumentally useful downstream of those. Computer science chatrooms are instrumentally useful too!
2. Identities can be like organizations (https://theanarchistlibrary.org/library/william-gillis-organizations-versus-getting-shit-done). They can cache themselves and capture the mind, imposing restrictions on how you think. They can take on lives of their own, creating obligations to make sure the organization lives on if you lose (at your goal). (Incidentally, the linked zine on getting stuff done is something I cite liberally in discussions of EA movement building). 

I don't think EA is doing anything that uniquely augments or complements the basic issues I have with identities altogether, but that would change if I thought too much was being invested in movement building.