I've never actually known what led to compromise of my card. Always stopped it, mostly before any charges other than the $1 authorization or something and one time after just one charge that made no sense at all.
Our stores have been involved in a couple of identity theft investigations since they always had video of the person using the card. In one, the card owner immediately recognized their housekeeper. The other one turned out to be the wife of an employee in a major credit reporting company. Talk about someone with access.
Think too of every time you've ever filled out a credit application. Those then float around in an office, in files open to many. Janitorial service employees have been known to rummage through files in offices.