Everybody loves a win/win solution. Of course they do. But how useful or achievable a concept is it? Is entering a negotiation with your counterparty's interests at the forefront of your mind really the best way to get what you need from a negotiation?
In truth, it all depends. It depends on the circumstances of the negotiation and what you want to gain beyond the deal itself. To earn respect in a marketplace you have to be fair in your dealings.