Om reported on May 21that Twitter had finally got hold of its $15 million second round, with a valuation said to be $80 million. Past backer USV is said to have contributed, as well as an unnamed main investor rumoured to be Spark Capital of Boston.

But no one seems to be any clearer about its business model. One commentator, Joseph Weisenthal at the Washington Post, suggests that the money is just buying time - plus a few servers to help with their notorious reliability problems. But this may not be enough. A recent post on the company's blog states that the root of the problem is unknown - something made clearer by Nik Cubrilovic at TechCrunch.

So what is Google doing all this time? If there is some really serious work to be done on scaling and on the business model, you can be pretty sure that they will be doing it with the Jaiku microblogging service they acquired last year. The money will help Twitter for now, but unless they can start generating real revenue soon, they will be trying for a third round within the foreseeable future, and wasting a lot of time in the bargain. Could this end up as another Netscape vs. Explorer?