Boy, is it ever.
http://www.livejournal.com/stats.bml shows that over two-thirds of LJ users are female. All those political bloggers wondering where the women are? Yeah, they're here. Over four million of them.
Also, the top of the age curve is in the 17-18 range, so those polibloggers best stay away, 'cause lots of them are underage.
There are more LJ accounts to people of high school age (15-18, over a million), than there are accounts to anyone over 21 (just over 910,000). There are almost as many middle school accounts (13 and 14, nearly 159,000) as there are accounts to people over 30 (around 160,500). A lot of users are undergrad age (19-22, over 830,000), but definitely not as many as high-schoolers.
All of these numbers are for accounts in general, not active accounts. Since only about 40% of LJ accounts are active in some way, I found myself wishing for some statistics that left out all the dead accounts.
Anyway, it was interesting to find out how close to the truth the stereotype actually was.