Found A Lost Credit Card Or Debit Card?

If you find a lost credit card or debit card, what's the best way to protect the person who lost the card? Nickel at FiveCentNickel.com described what he did when he came across a lost debit card near a theater. After not being able to locate a phone number for the card owner, he called the 1-800 number on the card and reported it lost. The rep placed a hold on it. Nickel then left it at the theater box office in case the owner returned. This seems to be the best approach. However, several commenters recommended to just destroy the card to prevent it from being used by a crook.