We had a gas credit card stolen and didn't realize it. After several tanks of gas in four days in an area that was not in our normal purchase area they called us. We didn't even realize the card was gone. They blocked the card and we didn't have to pay for the gas. That was Shell, by the way. I have also always called to let the bank know when we might be using the card in an unusual area.
Since people are not responsible for fraud committed with their cards, the banks aren't just being good watchers, they are protecting their own butts.