They've gotten much better lately, but I couldn't begin to guess how many times I've come home after getting off work at midnight, finding everyone in the house asleep, and all three entrance doors unlocked.
Since we moved Mary's business to our home, it's gotten a lot better. With clients coming to our home (most of whom are only casually known at best), she's gotten as paranoid as I am. Clients only come to the side door, are only let in by either her or me (after they ring the bell and we unlock the door), and they never set foot anywhere except the small exclusive area dedicated to business.
They are still a bit lax about locking the patio door after letting the dogs go out and come back in. I'm working on that one, but they don't realize the potential danger since they're "just right there!" in sight of the door.
I'm thinking a good practical lesson is in order.