When Twitter eventually goes public, it will be carrying the weight of the entire consumer Internet sector on its shoulders. Several years ago Twitter was one of four privately held consumer Internet companies that helped spark a startup renaissance (or bubble, depending on your viewpoint). The others were Facebook, Groupon, and Zynga. This quartet was indirectly responsible for the creation of online platforms for trading private company stocks. They were the reason that anyone who ever worked at Google suddenly fancied himself a freelance venture capitalist. Their sure-fire success sparked federal legislation to enable ordinary folks to crowdfund the next big thing. But a funny thing happened on the way to the afterparty: Groupon and Zynga both face-planted in the public markets, while Facebook's IPO was widely characterized as a dud (even though it raised a record $16 billion).