I've had an appallingly bad experience with Twitter's lack of community management. Please read this post for a summary of what I went through:
http://arielwaldman.com/2008/05/22/tw...
I think it's extremely important for Twitter to develop policies around their Terms of Service to stick by. In short, it's completely unacceptable for Twitter's users to be harassed to this level and have Twitter refuse to ban anyone for fear of being sued. Yahoo, Flickr, Pownce, and Digg do *not* take these kinds of TOS violations lightly and will ban users/content if there is even a question of harassment.
In fact, I would like to call out that Twitter can't be sued for banning users under Section 230 of the Communications Decency Act.
http://en.wikipedia.org/wiki/Section_...
As my lawyer wrote to me:
"It basically insulates any interactive computer service from liability for the postings of any of its users and gives it complete immunity anytime it removes user content because it is offensive. In fact, Section 230(c)(2) says expressly that "No provider or user of an interactive computer service shall be held liable on account of any action voluntarily taken in good faith to restrict access to or availability of material that the provider or user considers to be obscene, lewd, lascivious, filthy, excessively violent, harassing, or otherwise objectionable, whether or not such material is constitutionally protected."
This pretty clearly shields them from liability for removing posts and users who tweet offensive or harassing messages. Moreover, their own TOS says:
"We reserve the right to refuse service to anyone for any reason at any time."
Thus, legally, they are pretty much entitled to kill any account they want for any reason and there's not much legally anyone can do about it."