The acts of “pinning” and “repinning” (re-sharing a pin created by another user) have come under fire, especially in photographer circles, as tools for copyright infringement. Members can easily grab copyrighted works from photo-sharing or media sites and clip them to their boards. Pinned images often include attribution, but sources later get lost in the shuffle, and some members go on to use images on their blogs or websites. Plus, considering that Google is the second most popular source of pins, a sizable percentage images are likely misattributed.
I think a much more robust solution would be to somehow hard-code the original links / attribution into the pins, so there’s no way to accidentally strip away the source through repinning. One of the most interesting things about Pinterest is its ability to ‘curate’ material in a way that never claims its your own, but also gives some credit to the organizer of a board for their taste. If this anti-pinning technique really takes off, a huge value of the site would be squashed.