One simple answer to your question - speaking generally, as I know nothing about Twitter, specifically - is Twitter has yet to realize the expectations the _exi

One simple answer to your question - speaking generally, as I know nothing about Twitter, specifically - is Twitter has yet to realize the expectations the _existing_ investors placed on it. Real money was spent on real dreams, and the dreams failed to materialize. To give up on the BIG is to accept that their returns will fall sadly short.