Facebook (FB) needs no introduction. It's a social media site that outlasted Friendster and at the moment trumps Google Plus. In May of 2012, Facebook issued and sold 180 million class A shares at a price of $38 per share. However the stock spent most of its past year or so below the initial public offering price. The reason? People were skeptical that Facebook would be able to monetize their platform even with their 699M* active daily users and over 1.1B* active monthly users.
Disclosure: I do not have a position in FB.
* As of 6/30/13