Shannon's widget filters out obvious obscenities, but otherwise I just make sure I've got a reply to any negative comments. Seeing that dialog in there demonstrates a bit of authenticity.
Also, nobody's heard of my startup, so I feel fairly safe. Security through obscurity. :)
Thanks for sending that filter idea, I have never "understood" how to integrate twitter for marketing but that's a heck of a start - I'm planning to run some A/B tests on that . . .