Butting in to say: there's several places lots of people visit in fandom that have a large anonymous part but that we forget about because it's managed positively. Kink memes are one of them; gift exchanges, polls with results kept anon, anon commenting turned on for people crossposting, and love memes are a few others. For all these, an atmosphere of kindness and sharing is expected and encouraged from the start, and people naturally go with it. If we see someone being a brute on a love meme, our reaction would be "wtf? get out of here". But there's been a built-up of a different kind of expectation out of certain places (fandom secrets, confession places, etc) that I think encourages the other side. I've ranted a bit about this here.

All in all, I just wanted to add my two pennies that I think we can be a bit too quick in blaming anon memes in general. For me, the problem with certain places has little to do with anonymity and more with expectations and culture, which does link in to what you said about places set up explicitly to be nasty, just not the anon part.

Full disclamer: a great deal of my LJ contributions are anonymous and behind-the-scenes, so I felt like sort of presenting my point of view on the whole (though I also know what you meant). ^__^