I've always considered "hacking" relating to making a system do something it wasn't intended to do. You have to know the system well enough and be creative enough to go beyond its perceived limitations. I get a kick out of being creative; others get a kick out of having power over something. In either case, the real thrill is feeling alive and not feeling like a mindless robot.
It is funny we're having this conversation, considering Jason Calacanis's open letter, "Why I hired a felon" relating to one of his employees at Mahalo: http://calacanis.com/2009/03/05/why-i-employed-a-felon/