I understand that we could get very abstract about the concept of value, but what I meant to say is that many stocks have no guarantee behind them. If I buy a big mac, there's a pretty good guarantee that I can eat it, oil I can burn, a movie I can watch, virtual swords I can play a game better with. Value comes from how important these guarantees are to the buyer and seller.

Like FB, many stocks have meaningless voting rights, there's no buyback requirement, and you have no rights to company assets or earnings. You're guaranteed nothing when purchasing them, and so value comes entirely from opinion.