I admit I get a bit confused when people call for more net-nannying from sites like Twitter and Facebook. I get it more with Facebook, as they've long been making sure that what you post fits whatever "standards" they think it should be applying. Once they go down that road, it's reasonable to ask why if X violates their TOS, that Y doesn't.
But twitter is more a pure communications system. I get that people (cough women cough) face genuine harassment and threats there and I am not discounting the problem. Still it just seems like with a bit of intelligence you can give users control over what they see and don't see. Muting and blocking are good features (I do so miss when I could hellban people on the blog). Adding the ability to block all "new" accounts would probably solve a lot of problems. I'm sure there are other good ideas floating around.