We don't have filters anymore?
They've been using a URL shortening service with legitimate use, so filters probably won't help unless they decide to disallow the legitimate in order to stop the illegitimate.
Maybe even go along with the policy other sites use and don't let one post wonders link?
I'm not familiar with the code, but if it's not too much of a hassle, I would like to second this request. Though you can always ban AoL as well, just to be safe.