[zdw]

I'd love a website to swap these cards around...

Or, alternatively, some other social signal that people wanted to trade, similar to Button Men at conventions: http://en.wikipedia.org/wiki/Button_Men

[ambiguity]

That reminds me of the guy who tried to become the ultimate shopper by mailing people a copy of the UPC from his Safeway discount card with the intention that they would stick it over their UPC code. http://www.cockeyed.com/pranks/safeway/ultimate_shopper.html