It is certainly in no way legit to sell your miles and points. You should expect to lose both your points and any money that temporarily might find itself in your Paypal account. Worse if your account / personal details are used for identity fraud.

I can't recall off-hand for Hilton / Delta but, in addition to the comments others have made about usefully using them, you should be able to bequeath your points to a family member, so you don't need to be concerned about them being completely lost if you can't use them yourself.