Eh, for those who frequently hang around LJ (fandom communities in particular), I'm sure you've already got a glimpse of what's been going on. As far I know, the Harry Potter fandom's been hit hard, not sure about anime/manga communities, though I'm pretty sure they're on their toes.
For those of you who don't know, LJ users and comms listing pedophilia, shouta, loli, incest, etc. as interests are supposedly being reported by this groupWarriors For Innocence. This group (which reeks of sketchy vibes) basically claims to prevent online predators from striking.
Their method of attack seems to be first searching for users/communities by interests and then reporting listed names to LJ. LJ of course, is allowed to ban people/comms if they're posting "objectionable" material.
If you want to know more, this person seems to have compiled a fair amount of info and links regarding the issue as well as a list of suspended users and comms.