The SXSW people have learned this week that social networks are the new email.
The linked article doesn't say a whole lot, but as far as I can tell, I agree with the thesis. My sense is that it relates to the much larger problem that lots of jobs now involve an unmanageable flow of email and unrealistic expectations for responding to all of it. This problem is already at the center of writing about efficiency: David Allen's Getting Things Done and its many spinoffs, for example. But the deeper issue involves adapting asynchronous communication, which offers chronological flexibility at the price of obligation, to keep the connectivity of the digital world while removing the guilt.
That is, the fantastic thing about Facebook status updates, when used well, is that they give the reader a real sense of connection to the writer, but the expectation of reply becomes a more clearly voluntary option. It is like the shift in land mail from having the recipient pay postage to having the sender pay--but with obvious increases in the dispersal of information. I suspect that social networking is one early answer to the problem of using email too much and too broadly.