Last night, I went to a cognition/neuroscience talk, and at the end of the talk, the only contact detail the presenter gave was his twitter handle.
While brevity in communication can be useful, the more engaging outcome is that people have to formulate their ideas, post them someplace, and then tweet/dm you the link.
Does communication actually happen that way? Or does it just break down into tweetfests?
As for benefits, Twitter only (re)moves the spam problems of email while re-orienting our communications more towards group information.
Downsides include the registration requirements, and the need for external hosting of longer posts (arguably a nudge towards self-hosting and self-control of one's data).