Facebook doesn't own a serach engine, a browser, or Youtube. Google can basically collect all your internet activity and Google+ will be the thing that puts your real name on that data. Have you ever Googled something slightly shady? Would you be nervous if the Feds went to Google for that info?
Goodbye internet anonymity.
I just wanted to add that I don't think the internet is doomed as we know it...at least not yet. I just think it's interesting that a huge company like Google would admit something like this.