If you bought an original XBOX and didn't mod it eventually, you did yourself a huge disservice.
Also: If I'm paying $600 for a piece of hardware, I'm going to do what I want with it. Especially if it falls within the instructed usage at the time of purchase.
If Sony doesn't want me opening my PS3, they shouldn't have sold it to me. Same goes for Apple and my MacBook Pro, same goes for Microsoft and my XBOX. Unless you're going to stand over me with a gun at my head, or plant an explosive device in it, I'm going to open it. It's mine. I've earned that much.
That is to say, I don't particularly expect to retain all my rights to using it having opened it. I don't expect Microsoft to take kindly to me installing shit they didn't approve on my XBOX. I'm not going to cry when I can't take it online anymore. I still think I have every right to open the thing up and do whatever I want.