I have just had my feelings stung, and I don't really know how to deal with it. I just discovered one of my 'pay-it-forward' items listed on ebay.
I guess it's the individuals item after it leaves my hands, and therefore they can do what they like with it. However the thing that bothers me most is that it's really not in the spirit of the whole pay it forward concept - maybe if they didn't like it, they could have paid it forward to someone else.
Disappointing, and actually - it kind of hurts.