There are only two parties who would have interest in launching such an attack: the stupid kid at school who couldn't "h4ck" into the site and wants to show off to their friends anyway... and the "competitor site" who wants to attract customers because they are "so much more secure". Newsflash: Nobody can successfully block a DDoS attack. Either the site will throw out legit requests during such an attack or... wait, that's PRECISELY what DDoS wants the site to do anyway. Essentially nobody who runs a website can do anything against DDoS except hope for law enforcement and ISP cooperation.
I wouldn't be surprised if the current DDoS against LiveJournal was initiated by some well known site with "book" in their name who already had the guts to try to trademark "book" AFAIK.
So... I've paid for my LJ account and I'll continue using it. And I sure hope my friends will do the same. Don't give the attackers the satisfaction of leaving.