check out this patent application apple filed:

http://www.ipwatchdog.com/2009/10/22/jobs-and-apple-seek-patent-on-operating-system-ad...ising/id=6761/

The operating system is configured to present one or more of the advertisements to users of the computer device. In some implementations, the operating system can disable one or more functions during the presentation of the advertisements and then enable the function(s) in response to the advertisements ending. That is, the operating system can disable some aspect of its operation to prompt the operator to pay attention to the advertisement.
how do you like them apple(s)? (<--sorry, couldn't resist)