I'm not sure this is entirely right. I have a public profile on Google, but it didn't announce the people that I converse with on a regular basis before Buzz (at least as far as I know).

I turned off Buzz because I don't see a value in it for me, but before that I had to search to figure out how to make it so that my contacts were not made public. I was a little irate because it represented a significant portion of my client list which is more than a little bit frustrating.