That's assuming a user input their real details in the first place.
Google of course knows more about you than you probably do yourself. If you have a Gmail account have it open and do a Google search in a separate window, Google will remember all about it.
Close it all up and then open up Youtube. Chances are that whatever topic you searched for in Google will be proferred up on the video site, whether you want it or not.
Blinking cheek. µ