Social networks essentially obsolete email. This is just a bridge to dead technology the way email-to-fax service was a bridge to a preceding technology, the way services to receive and deliver faxes/telegraphs were a bridge. The next step forward is distributed social networking - getting you out of the "walled garden" for good by breaking down the walls. When any individual or micro-network can communicate with any other via a shared protocol you'll officially be out of that paradigm. Several projects are promising that (notably Diaspora).

*If* Facebook makes this move, it is a sign of an attempt to consolidate a strong position in aging technology because it has reached a dead-end in innovation. This is the kind of move that a mature business makes, one that is no longer interested in breaking new ground. It's a defensive play, and a good one, but also a signal that we'll no longer need to bother looking to 1st generation networks like Facebook for an indication of where things are going.

Yeah, with their attitude toward their users privacy the first thing I want to do is give them access to ALL my information and emails...