Google Buzz is the loudest party I've ever been forced to attend. It's not because there are too many people invited but because of all the chatter. I'm following only 40 others. And even if I wanted to follow a few hundred more, my network's too small. But these 40 contacts all have their own friends, and even though I've never met most of them, Google is making me hear their thoughts.
And that dynamic makes Google Buzz a fundamentally different social network than Facebook and Twitter. Those networks, of course, are also filled with noise. But Google pushes the comments of your friends' friends (we'll call them secondary friends from here on out) into your Gmail window, alerting you whenever a secondary friend has responded to something your actual friend has written. This is a small quirk, and only mildly different from similar features on Facebook and Twitter. But it's Buzz's biggest one. Google's network will live or die depending on whether people like all that chatter.