Originally Posted by RJB

They are not transferable .... but how would they know? Make the booking in your name, and your friend shows up and claims to be you. Lend him your credit card for swiping at check-in (no signature required) but make sure he pays in cash when he leaves. Or, he gets his partner to swipe her credit card and pretends they are not married, which is why the surnames are different.

There is some risk, but you should be OK unless you booking in a country where the hotel is legally obliged to take a copy of your passport upon check-in.