Ever heard of credit card-shaving? Neither had I. I guess some people with bad intentions and a lot of time on their hands just try different sixteen-digit number combinations until they find one that works. Then they shave numbers one-by-one off of other cards (credit cards, debit cards, gift cards, etc.) and glue them on a new card...which they then use to make illicit purchases.
Wacky...yet creative!
http://www.oregonlive.com/news/oregonian/index.ssf?/base/news/120676296493670.xml&coll=7&thispage=1