It was common knowledge that Apple’s new AppleTV was running some sort of variation of iOS under the hood, especially since it uses the iPhone 4 and iPad’s A4 CPU for silicon horsepower, but TUAW has confirmed it: the AppleTV is an iOS device, and therefore jailbreakable using existing techniques… although since there’s no local storage, I would imagine any AppleTV jailbreaking would mostly focus on improving functionality by beefing HD output up to 1080p.
Confirmed: New Apple TV Runs iOS