Twitter has no business model. But it’s got the users – some 4.4 million of them as of December. And at least one VC is prepared to invest – at a $250 million valuation according to TechCrunch and MediaMemo. The exact amount of the funding wasn’t specified.

The funding isn’t an entirely a surprise. Facebook offered to buy the micro-blogging company in November 2008 for $500 million. Twitter turned it down.

The company has raised about $20 million in total, with the latest cash infusion of $15 million coming in June 2008 (that supposedly was at a valuation of $100 million).

Investors to date include: Spark Capital, Bezos Expeditions, Union Square Ventures and Digital Garage.