After seeing the responses to Robert's dilemma of his nude model wanting back her pictures I was not surprised. However had this been a professional forum (people that did photography for a living) the responses would have been 99-1 in favor of telling the people politely that they have no right to even ask.
I had been a member of different portrait associations over the years including Professional Photographers of America, Professional Photographers of Canada as well as a bunch of others. These associations and others pay lobbyists to monitor and fight for photographers rights as to copyright etc.
Quite a few people on this site are strickly scenic photographers and I'm wondering if they would feel the same way if they photographed say a farm building on a great vista (a la Moonrise over..) and were approached afterwards by the farmer and he demanded back the prints and negs. This is not too farfetched as if this farm building was identifyable as his, he has a case. But for the sake of argument would you be as willing to give away your work. Even if the work was not great, or not your best, would you cave in under this pressure. Would the fact that someone was angry that you took their farmhouse cause you to give them your work?
A number of people have cited goodwill or not worth the trouble, or being a nice guy etc as a determing factor. We as a community and profession have always been very self conscious about ourselves and so willing to give in to demands like this. I don't think any other profession is the same way. Do architects give away their blueprints, do jewellery designers give you the mold with the piece they designed?
I can remember when I used to shoot wedding and after they placed their order they asked can they have the negs. I said no, we retain the rights etc. and they asked a perfectly legitimate question. "what do you need then for?. Well the answer is I don't need them. But they are mine. In fact a lot of beginning photographers give away their negs afterwards, which makes the rest of us cringe.
I guess my point is, they are my property, I spent a lot of time learning to make them and they don't now, or ever, belong to the person that is in them. And would you feel the same way if someone demanded your work because they, or their property are in them.