As you have probably heard by now, the EFF has convinced the U.S. copyright office to grant exemptions to the DMCA, which mean that users of phones like the iPhone can jailbreak them. While it may be legal to do so, Apple still doesn't want you to.
Leander Kahney at Cult of Mac received this statement from Apple on the matter:
"Apple's goal has always been to insure that our customers have a great experience with their iPhone and we know that jailbreaking can severely degrade the experience. As we've said before, the vast majority of customers do not jailbreak their iPhones as this can violate the warranty and can cause the iPhone to become unstable and not work reliably."
Kahney also speculates that now that jailbreaking is officially legal, we may see a "cottage industry" of unofficial app stores pop up. That could be interesting, particularly since Apple is notorious for being very strict with the apps it allows in the App Store.
ComputerWorld asks if it is now legal to start a business around jailbreaking phones. Mitch Wagner writes, "Would it now be legal to start a business jailbreaking iPhones for other people? Could you legally buy iPhones from Apple, jailbreak them, and then sell them? weaKnees does just that kind of business for DVRs, it sells TiVos hacked to include larger hard drives than the manufacturer standard. We've had one of their hacked TiVos for three years, it works great. If weaKnees decided to branch out to selling jailbroken iPhones, would that be legal?"
Keep in mind that part of Apple's statement about violating you warranty.