>Add a feature that allows admins to restrict registration for set periods of time. That might make it easier to deal with alts since no new accounts can be created.
We actually have that currently. But our team has noticed that it appears to give spammers a "win" by visibly taking down the site for anyone who wants to join, so we've implemented new spam detection mechanisms. So far, we're pretty pleased with their ability to shut down attacks pre-emptively, or quickly after they've begun. And we're tweaking them all the time to make them intelligently block spam even faster.
As for a taste of things to come, expect Russian spam bots clogging up the News section to soon be a thing of the past