To play devil's advocate, I think the "12 year old girls being drama queens about their friends list" prejudice is widely held in the blogosphere as a whole, which probably means that a) there are a lot of people who do assume LJ is full of crap, and b) even the people who don't assume that know that the people who do won't take a link to LJ seriously, so avoid linking to it, even if there's an individual post they think is good.

OTOH, I do think a lot of LJ is crap by the standards of the blogosphere, simply because it's a weird hybrid between a blog and a diary that you let everyone read. LJers are forever posting memes and cute pictures of cats and whatever silly thing pops into their head, whereas the really popular blogs are the ones with a strong focus on one topic. (Where comms fit into this I'm not sure.)