Apple has released a software update to the Apple TV. The full release notes are available here. It's likely to be overlooked by many, but this release is a very big deal. Taken from Apple's release:

Save multiple iTunes accounts and switch quickly between them.

This is the first iOS device to allow any form of multiple account log in. A very big deal indeed. Let's hope this is just a start and future iOS software updates for other devices will include multiple account support.