This in particular. It took me a very long time to recognize how important this was, but looking back the very best social spaces I've ever been in have all had reasonable standards of moderation with moderators who actually paid attention to the various conversations going on. That's not to say that all spaces with moderation standards are good, but I can't think of a worthwhile social network with hands-off or primarily user-driven moderation.
Trouble is, we haven't figured out a way to scale "good moderation" up to something like Facebook scale, and organizing a mass exodus from large social space is a lot harder to do en mass unless you have a Digg v4-scale unforced error.