Well, it seems I had to change my personal rule about not deleting any comments from my LJ, ever. It seems that spammers have discovered LJ -- they find someone's account that has been inactive for over a year, hack into it (I'm assuming), and use it to post comments filled with Viagra or other ads. And it turns out that the only way to report spam is to click the "this is spam" option while you're deleting a comment. So yah, I've been deleting comments filled with spam. I will still only delete these comments, not others.
And really, the LJ spammers haven't been nearly so prolific as the Orkut spammers -- every day I get another Orkut message with some random person who doesn't even speak my language wanting to friend me, or a scrapbook entry advertising crap.
But really, I mean, I'm not surprised that spammers have found the new venues for depositing their stinky messes. I'm just surprised that I'm getting socked by it so suddenly.