While I agree that naive technological utopianism is worrisome and we need to be discussing the social/psychological impact of our inventions, I can't say I would draw an equivalence between Twitter and something like cigarettes... if used in moderation, I think services like Twitter can be very useful to some people. We do need to weigh the costs vs. the benefits, but just as blind acceptance is bad, so is blind rejection... having this discussion is a good start though.