This New York Times piece does a good job of articulating some of the privacy concerns that accompany Google's default Buzz deployment. And Danny Sullivan, a specialist on Google interviewed for the article, sums up my feeling on the matter very well:
“I don’t think people expected that Google would show the world who you are connected with. And if there was a way to opt out, it was really easy to miss.”
If you feel the way I do and want to purge your Gmail of unsolicited social networking advances, you may want to check out this little Buzz-Off guide put together by the people at CNET. Apparently the little "turn off buzz" button at the bottom of your Gmail screen doesn't quite get the job done.
This showed up with a GIS for "buzz off." I think it keeps flies off the horse. I want one for my Gmail that protects against Facebook.