Apple is planning a major iTunes announcement for tomorrow, which has the Internet in an uproar about what the iTunes deal might be. The most likely scenario seems to be a cloud-based feature in iTunes, that will allow users to stream their iTunes libraries from anywhere.
The Apple web site had a minimal message today that read "Tomorrow is just another day. That you'll never forget. Check back here tomorrow for an exciting announcement from iTunes."
This could have been what Apple bought Lala for, last year. Follow that with the completion of a new data center that was recently built by Apple, and you've got enough information to fuel a firestorm about a cloud-based version of iTunes.
This is backed up by the recent iTunes update to version 10.1, which includes references to "iTunes Live Stream," which looks to be a streaming service built into iTunes as a core functionality.
Alternate theories include an iTunes subscription plan that would allow users to gain access to everything that Apple sells through iTunes, for streaming instead of purchasing a download. Another theory is an Apple music streaming service that would give iTunes users the ability to subscribe to an all-you-can-listen-to service like MOG or Pandora, for a monthly fee. This theory has its doubters, including Apple Insider, who says that the licensing for that is not in place.