This is the advertisement from google itself... essentially it's a social network integrated right into gmail (sort of a twitter/gmail mutant)
"Go beyond status messages
Share updates, photos, videos, and more.
Start conversations about the things you find interesting."
The problem is, that once you activate Buzz, google does this with the CONTACT LIST of your gmail. Now try to think of all the people you have in your gmail. Friends, relatives... teachers ... your boss... that starts to get creepy. Why the hell would anyone want to share their personal information with everyone?
Another problem is, that google does all this automatically, without even giving you a chance to customize things before it all starts. Sure, you can change settings, filter people, and turn off what you don't want... but the fact that everything is turned ON by default, without asking you is just wrong.
http://www.crn.com/software/222900037;jsessionid=M1GMX2ISLXQTXQE1GHOSKHWATMY32JVN
http://www.pcworld.com/article/189081/google_buzz_criticized_for_disclosing_gmail_contacts.html
I won't even go to other very serious flaws that are unsettling about this "service". Like the fact, that google by itself took photos from people's Android phones and uploaded them as profile photos for Buzz. Other things are inside the links up there.
I feel like a guinea pig, being experimented upon. Also, it feels like google just attacked and destroyed one of the most private places you can find on internet - your email account.
If google continues to experiment like this on their users, I think I will consider leaving their service (hell, I think I'll even prefer yahoo over this abuse of personal space. And Yahoo already is abusing personal space preety much).
One other thing, that really shows the situation. Try to put "google buzz" into google - the top page is a guide how to totally disable buzzing :-)

Well, it didn't seem too hard to turn off the majority of Buzz, but really, this is what they should have done with Wave... stuff it down people's throats in the gmail interface. Doing it with something like Buzz does feel wrong, doesn't it?
However, the gmail interface is far too helpful for me to consider using anything else. I've got Tasks, I've got the Calendar, I've got chat.... they offer a good service. Having Buzz in there is okay, I guess... the only problem is the way they chose to handle getting it started.

I just ignored it and now I'm glad I did. I don't do social networking websites.

A lot of people have already removed things like Twitter and Facebook accounts from Buzz because it shares everything with everyone. Some sites have also raised security issues about the whole service. Google have definitley not thought the service through properly.

No. My stuff is already public in the first place, so whatever.

It was incredibly stupid of Google to not make the service an "opt in" feature. I already completely disabled it, not that I actually use my Gmail account for much anyway.

Right, that's for Friendster!

it's not like I want to fight against social networks. I am an active user of facebook, have a lot of things public and so on. Also, I don't think I have anything in particular to hide.
What I don't like about this is, how google is forcing these things on people, sharing everything with everyone like Delixe said.
Here's one more article, I think this one got the issue most objectively from what I've seen so far :) Interesting read...
http://www.msnbc.msn.com/id/35351343/ns/technology_and_science-tech_and_gadgets/

I saw I was suddenly subscribed to a bunch of people's "buzz" tweets or whatever and that a bunch of people were subscribed to me. I then scrolled to the bottom of my gmail page and noticed a handy link that says "Turn Off Buzz". Problem solved.

I really don't like social networking, and the idea that some anti-privacy social service gets integrated in a service where ALL my mails are stored is...disturbing.

Thanks for pointing that out. :D

WHAA? Then how on earth do you look at pictures of a friend of a friend of a friend's cat?

Hmmm, first time I logged after it was introduced, I was given the option to use it or not. Not very forcey.

Google's stated goal is to obtain all the information in the world.
That includes your email, your friends, your habits, pictures and maps of where you live, and any STDs you might have had.
And all of it is to be made search- and shareable by default.
Chew on that for a moment.