Hindsight is 20/20. Today's featured commenter, madox, has it in spades, on Twitter's lack of a business model:

Owen, I'll take a different approach to the "premium service" concept: People that use Twitter now, or have heard of Twitter, expect it to be free. As soon as Twitter starts to charge business customers for their service, they'll simply stop using Twitter because the current mindset is that it should be, and obviously can be, free.

Twitter, from its onset, should have created a tiered pricing model for various account types; this would have eliminated the current user expectations that it is a free service.