Here are 2 Google Buzz privacy concerns you need to know:
1) Google Buzz automatically has you follow, and be followed, by everyone in your contacts list.
With Google Buzz, you automatically follow everyone in your Gmail contact list, and that information is publicly available in your profile, by default, to everyone who visits your profile.
And within your profile, that list is available with “follow” links!
2) Google Buzz Broadcasts Your Email Address
With Google Buzz, one of the central points of focus is your Google profile. So let’s say you’ve customized your Google profile page with the vanity URL Google offers at the bottom of the page. Wouldn’t that URL also be your email handle?
So anyone who does an @ reply to you would, in essence, be broadcasting your emailing address to an unknown, massive audience of followers.
Probably the biggest concern that I have, and why I decided to turn off Google Buzz, is that everything is “opt-in” automatically for me. That means, by default you are opted-in to follow and be followed by everyone in your contact list. And most frightening is that your list is publicly viewable in your Google profile.
At least with Facebook you have a double opt-in required in order to become friends. Both parties have to receive and accept an invitation before becoming friends and making news streams available.
I think that Google Buzz is about to face some unforeseen scrutiny, and this might just be one Google product that falls flat on its face.