Most online credit card fraud is caused by lost credit cards so if someone found a credit card they wouldn't be able to use it online
Sorry but this is far away from reality. Just check the news and see whats going on out there!
http://www.cardcops.com/
The guy who runs this site is an idiot, but thats not the case right now. But the fact is that one guy can steal up to 100 credit cards in a couple of minutes, by hacking some shop site for example. But no one finds hundred´s of lost cards in a few minutes at the streets.