Well, you might still be able to hack the Xbox 360, but don’t expect to be able to return the beast when you mess up and break something. The case is going to be free of screws and many little labels will let Microsoft know if you decided to ignore their warnings and try anyways.
I don’t know about you, but if I pay over $500 for a console, I am not going to try modifying it, atleast until I have beaten a game or two.
Source: Joystiq