Apple is just trying to protect the user experience for their product.
Yes, it is ours to use and do with whatever we want once paid for, but.........
Every jailbroken iphone user will complain and tell somebody that their phone always freezes up or isn't working right.
They are not going to say in most cases it freezes, because I jail broke it!
That info makes it look as if it is Apples fault that things don't work.
Like when people wreck their cars and say the gas pedal stuck at the exact same moment the brakes failed?