General advice for mariedm - be prepared to ban quite a lot of accounts at their first offense, think about IP bans, email verification, banning proxies, etc.
If some of the various online communities of, um, hard to pick a term here that someone won't take offense to, but you probably know what sort of communities I'm talking about - if they take an interest in your site, you'll need heavy defense, and quick reactions, to avoid major disruption. Maybe all comments from newer accounts should go through moderation before being posted? Or have that as a switch that can be turned on when the attacks happen?
If some of the various online communities of, um, hard to pick a term here that someone won't take offense to, but you probably know what sort of communities I'm talking about - if they take an interest in your site, you'll need heavy defense, and quick reactions, to avoid major disruption. Maybe all comments from newer accounts should go through moderation before being posted? Or have that as a switch that can be turned on when the attacks happen?
Good luck.