My 10-word summary of GDC 2010 was just the word "Facebook" 10 times. Game designer Soren Johnson quoted that, and wrote a long post that gives a good sense of what's going on there. He covers the phonomenon from several angles, it's a good read.
And while we're at it, here's the new Facebook page for Sirlin Games. It would be cool if you clicked to be a fan so you can see various new art (coming soon!) and other developments. Thanks!