Apple says jailbreaking will void your warranty.
Yesterday the Library of Congress said that if you own a smart phone, you should be able to run any kind of software that works on that phone even if the company that makes it, Apple for instance, doesn't approve of that software. It's your phone, after all. It's a process called jailbreaking your phone.
This was a pretty significant decision in terms of the future of licensing and the entire concept of ownership (think about all that stuff you get from iTunes that you don't really own, you just use it with Apple's permission). But the process of actually jailbreaking your phone is an arduous one and few people are likely to bother. But big picture? Years from now? Huge.
Now Apple says well we may have to go along with that but we don't have to like it. They're saying that if you jailbreak your phone, you're no longer covered under warranty.