heres an intresting read on what they have done or not
http://www.guardian.co.uk/media/pda/...r-making-money
Premium accounts
What they said: Twitter co-founder Biz Stone said in August that the company would charge users for "premium accounts". In November, Stone said the plans were well on their way and that a pay-for-package offering that would include verified streams and analytics would launch by the end of the year.
What they've done: The company has not started charging for premium accounts. However, it has rolled out free business-friendly features like "contributors," which helps differentiate between multiple users of a single Twitter account.
Mobile deals
What they said: At our own EconSM conference, Kevin Thau, Twitter's director of mobile business development, said the company would make money from handset deals and also by getting some sort of cut of the carriers' data business.
What they've done: Twitter has dozens of relationships with carriers—financial details of which are unknown. The company did, however, link up with Peek in November to launch a $99 device designed for the frequent Tweeter.
Search
What they said: Thau also said at our conference that Twitter would monetise search "in some way".
What they've done: Twitter has since licensed its stream of Tweets to Microsoft, Google and Yahoo – which are all using the data to add real-time results from Twitter to their search engines. The Microsoft and Google deals alone are believed to be worth as much as $25m.
more on the link above