Microsoft knew that their Windows Phone 7 would be poked and prodded until someone hacked it. Of course, they don’t want people doing it and have released their take on 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.”