Most of us send out the same card to each person, but you are free to send out different cards to different people. Personally, I think part of the attraction comes from the variety of feedback I get from people in response to the same image.
Originally Posted by polyglot
In addition, if you do print traditional analogue prints (and there is more flexibility in this exchange than just about any other APUG event) part of the joy and challenge of making multiple prints is dealing with the minor variations inherent in the process.
Hope this helps.