But instead of the photogenic smiling faces, it’ll probably be your friends’ ugly mugs.
Whenever yourself or a friend comment on, follow or +1 a page while logged in with his or her Google account, that content may then be used alongside Google’s future advertising. This is clearly a horrible idea but not unexpected from Google (considering their recent moves towards the proliferating of Google+). However, you would glad to know that it is entirely optional and you can easily opt out.
On other privacy infringing news, you can also easily opt out from Facebook’s version.