The big question: If Twitter were built today would it have used the same infrastructure? If the answer is no that means Twitter in its short life is already saddled with legacy technology and that’s a project management nightmare. You only get one shot at an IT greenfield and Twitter may have guessed wrong.
I have no idea if this is true. But as I’ve written recently, there’s a vibrant market for miniblogging. And if Twitter doesn’t nail it, someone else will.