SafeHarbor are the eBay police department. If you break the rules, commit fraud or try to buy something you're not supposed to, they'll be after you.
When You Don't Pay.
This is the most common rule buyers break, it's all too easy to just change your mind and try to get out of the auction. eBay regards every auction as a contract, and will punish you if you don't go through with your end of the deal. If you decide not to pay then expect to get a few nasty warning emails from eBay threatening you with banning if you do it again. Not to mention, of course, that you'll get a big negative 'DID NOT PAY' feedback comment from the seller.