If I go to a viral video, and I see comments on it from people I actually KNOW, I personally think that would be really cool.Or really creepy.
a- Imagine you're going to a real world bookstore. You look at the back cover of a few books and all the reviews are by your Google+ "friends". Customized for you to increase the chances you're buying it. (If ads are going everywhere and you try to ignore them, what will be left?)
b- In your holidays you're traveling to another continent. After arriving, you're surprised that you see the faces of your Facebook stalkers everywhere. Would you like that?
c- Your government rolls out new mandatory ID smartcards for both the offline and online worlds. Soon after they require everybody to sign their TCP packets with those cards. A friendly smiling illustration of a computer asks you to swipe your card to login to your OS. Have a safe journey online!