Having read the news
and detailed analysis by friends
, I have concluded that Google Buzz was implemented in a recklessly unsafe manner by Google. There is currently absolutely no way to opt-out.
The "turn off buzz" link at the bottom of gmail only turns off the buzz widget in gmail. I have since unfollowed everyone on Buzz and am summarily blocking anyone who attempts to follow me and I suggest you do the same. C|net has instructions here
Edit: Deleting your public profile now pulls you out of the system. Note: You were added to their system automatically, even if you clicked "Nah". Current Mood: annoyed