ChevronWP7 jailbreaks Microsoft's new Windows Phone 7. Luckily, a statement released by Microsoft gives the impression that they aren't intending to play the same cat-and-mouse game with jailbreakers that Apple does. They aren't encouraging it, of course, but they also aren't flat-out condemning it.
We anticipated that people would attempt to unlock the phones and explore the underlying operating system. We encourage people to use their Windows Phone as supplied by the manufacturer to ensure the best possible user experience. Attempting to unlock a device could void the warranty, disable phone functionality, interrupt access to Windows Phone 7 services or render the phone permanently unusable.
[Geek.com]