- don't friend them (they may abuse personal information in your friends-only posts)
- ban them (so their public posts don't gain PageRank from the "friend of" link on your profile)
If anybody has more of a clue of what's going on and a better way to deal with it, I'd love to hear about it.
In other news, Twitter apparently has developed a problem with spam accounts "following" people, which is another way to get an automatic link back to your page. I got hit with 5 overnight. The way you can tell they're not legit is, I'm just not that popular among the "GET RICH QUICK BY ENLARGING YOUR PENIS" set.
Meanwhile, a certain Valerie Stevens of Uxbridge, MA is an "evangelist for new and emerging marketing trends" (apparently this is the sophisticated way to say "spammer"), and her favorite new trend seems to be indiscriminately following thousands of people on twitter, then only keeping the hundreds who (presumably more or less automatically) follow her back. Way to keep that signal : noise ratio good and high there, Valerie.
Kiddies, this isn't what Twitter (or LJ) is for. Either they'll figure out how to stop you or you'll break it, and either way you suck.