Is Google Buzz the next big thing in social networking?

Tuesday, Google announced Buzz, a social networking add-on to its popular and free Gmail service.

The buzz in the blogosphere is that this is a shot across the bow of Twitter and Facebook. Though Google has partnered with Twitter and Facebook in the past and continues to do so with Twitter in Buzz, Facebook is conspicuously missing from the Buzz interface.

So, why Buzz and why now?