I'm pretty sure mine is off a card receipt from a place that I've shopped or eaten. I'm normally quite careful about where and when I use my cards but I guess you can't be careful enough. My brother has had somebody go wild on his card once and spent about $1000.

In theory it should be possible to find out who has my card details as they signed up for a dating site. The charge was for an adult verification system they've got on this site so they must know who it's for. Doubt my bank will do anything about it though.