Two years ago I received a fishy e-mail saying that my credit card had been blocked because misuse had been detected.
As my complete name was in the email (which I don't use to write anywhere) I decided to call, but not the number on the e-mail, but the number on my credit card.
They told me to call that number, as it was a real email.
As I travel quite a lot and have to pay at hotels with the card, someone had got the data of my credit card. First they did a 1 $ payment to paypal, and after that it was about € 700 on different e-shops.
Luckily the bank blocked the card. But I had to report the theft to the police to reclaim back my money. In the end of the € 700 only about € 150 made it to my account, but that was a scary experience, as I was abroad when I was notified.
Anyway, as for today I block the card for usage in any country that is not where I am, and get e-mail and message notifications for every payment I do with the card.
You can never be careful enough. Although I never enter my credit card details in any e-shop which does not use encryption, and don't save my credit card in any e-shop to "pay quicker" the next time, I got hacked.