I have mixed feelings about this. One of the awesome things about Android is the ability to root pretty much any phone so you can trick it out even more than usual (which I've never done, but still, it's great to have the option). On the other hand, you can seriously mess up or brick your phone if you don't know what you're doing, and sometimes even if you do know what you're doing. If the warranty states that rooting the phone may void the warranty, it seems reasonable from a business standpoint for the phone manufacturer to know if it was rooted at any point, and if that may have contributed to the phone not working correctly any more.