Personally I have a hard time seeing how Twitter will be monetized. Obviously the founders of the company do too. They were quoted at a recent conference as stating "We don't know." when asked when the company will make money.
That is cool as long as they are not going out and trying to get money invested in them. If I were investing in a company and their business plan, at least in public, was "I don't know" I think I would hesitate a few moments before writing the cheque.
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