Anyone who hacks himself into a closed operating system, is doing something illegal. It didn't stop Microsoft from inviting three hackers who jailbroke Windows Phone 7 to the company's headquarters.
The hackers were not in Redmond to be punished for their deeds. Microsoft wanted to exchange thoughts with the group of hackers, so Rafael Rivera, Chris Walsh en Long Zheng came to Redmond for a meetup with Brandon Watson and other member of the Windows Phone 7 development team. The even created a funny t-shirt for the hackers.
Good side
Microsoft shows its good site with the invitation. It can benefit from the work of the hackers, as their action show the vulnerabilities of Windows Phone 7, and as such can help Micorosft improving the OS.
Source: Istartedsomething.com