In any sort of negotiations, one of the tactics is to tie your own hands. If you cannot concede, it forces the other side to do so. So I was wondering, what would happen if, when someone took hostages and demanded an exchange of prisoners, you took the list of those they demanded released and summarily executed them? Suddenly, their demand has become impossible to fulfill. They'd have to come up with secondary demands or kill the hostages. If they kill the hostages, they've just thrown away their only negotiating piece.
It gets more interesting, however, when you consider the negotiating counter-moves. Would people demand lists of prisoners in the future if they knew that was the result? Would people take hostages and then demand the release of prisoners from another faction just to have them killed? How would you counter such a move?