As the most appreciated VC not just by me incidentally but by the HN I still don't get his points investing in companies. And my question would be in fact: Doe

As the most appreciated VC not just by me incidentally but by the HN I still don't get his points investing in companies. And my question would be in fact: Does anyone knows what drives VC investments in companies / products like Facebook, Tumblr or Foursquare? Yes, the profit, BUT who will generate that profit? We, free users of these services? How?