A few days ago, I saw a segment on the news where thieves are breaking into gas stations in the middle of the night and stealing gas.
With gas prices continuing to climb, I figure people are going to get more and more desperate, and eventually they're going to start siphoning gas from people's cars.
In that regard, I highly recommend you invest in a locking gas cap for your car. I bought one for my car over the weekend. It cost $14.95 - a small price to pay for peace of mind!
Dale King