How about... a percentage of the fee for each gift goes to charity, maybe? Then people can give virtual cookies to their mates and to a good cause.

Going further, people could nominate charities and have a monthly option of three. (One of my local supermarkets does this with a token system and a box by the exit. It's very well-received). There would probably have to be sufficient traffic to justify a rotating option, and I'm not sure how it would work with non-US charities, but I'm sure we could think of a list of twelve international charities people would be happy to donate to.