There has been very little public comment about Microsoft's deal with Comcast. (This is not because I said everything there is to say about it.)

But there have been two follow-on stories that help explain it. (The image of the Comcast logo is from CNN.)

First, Microsoft is showing off server software (for 2005 shipment) that allows federated identity. That is, you sign-in to one site and can be signed-on to many others. This could solve a growing problem in the newspaper industry, papers demanding registration so they can track users and keep up ad rates, but losing most subscribers (and their influence).

Second, Comcast has been revealed to be the chief source of spam in the U.S. According to Declan McCullough, malware is infecting users of Comcast's cable modem network, turning user computers into spam zombies that are infecting everyone else in the world with spam. (That's another CNN illustration, by the way, from a fine story on the problems of identity.)

So. Microsoft is showing it can solve an Internet identity problem. Microsoft has signed a deal to provide media software to Comcast, software that relies on identity. Tie those identities to e-mail, make Microsoft responsible for regular updates of Comcast user software (in part to get rid of this malware), and a lot of problems get solved, problems Comcast can't solve on its own.

That's the theory, anyway.

Now Microsoft must deliver.