In addition to the enforcement issue: From time to time people have asked me whether they could sell their accounts or use them as collateral because they have an emergency need for money or have come on hard times. I'm not going to tell them they can't do this. It's your account and you can do what you want with it. I find it pretty distasteful (it's like selling your identity), but the act of selling your account does not itself hurt anyone else, and in fact scams via account sales are very rare.