NBC has launched NBC Direct, in a move to deliver some of its biggest shows free and ad-supported through NBC.com and compete with Apple's iTunes Store. The service has some limits, though. Downloads can only be watched for a week after the show airs on the network. And you need to use NBC's Windows-only software - although the company said it will eventually allow the programs to be watched on Mac computers and portable devices.

The entertainment industry is beginning to learn the hard way that viewers are increasingly moving away from traditional television viewing, and thus they are throwing multiple business models out there to see what sticks. The move by NBC seems pretty reasonable, too. There will probably be a lot of people out there who just want to see a show once, on demand and for free, even if that means having to watch a few ads.

The network is not committing to a single platform, however. NBC has struck a deal to sell its shows through Amazon Unbox and is also working with News Corp to launch a new online video service called Hulu. But perhaps the network is hoping that its ad-based model can be more profitable than video sales. The company says it'll begin beta testing the new "NBC Direct" service in October.