cause right now any time with an iphone 4, when you want it jailbroken you have to have it connected to a laptop in order to run cydia, and if your battery dies in the middle of the day or you need to restart your phone you have to run a program on your computer to re-jailbreak it. So if you want the chance to be without a phone until you can get to a pc and rejailbreak go right ahead lol
yes it will cause problems, read up on things before suggesting things, and you cant install 4.1 as apple has stopped signing it for install, so that wont work