The thief might not even know he had a wallet.

Whilst cruising Boing Boing I came across these sweet wallets.
One of the four designs below:


Say you left your wallet in your car or dropped it in a public place. The not so savvy klepto probably would see it as a plain piece of paper. Thus missing a prime source of monetary gain with which they could continue their nefarious rampage. Of course I'm going to pick up every scrap of paper I see from now on. I might get lucky!