What is the major difference between White-hat and Grey Hat SEO?

Grey Hat always seems to be those that are constantly trying to push the limits of what White Hat really means. These folks seem to live in that area that is the difference between the "letter of the law and the spirit of the law." These folks seem to spend more time on gaming the system than actually producing great content or doing the regular work needed to make a site great in the eyes of humans and search engines, although oddly, they're usually perfectly capable of such work. Grey Hats are those that break the basic speed law, but never driver excessively (but are still pissed at the cop when they get busted).