Well you know. we are guilty. We have a screened in lanai around the pool and spa. Since our cats love to prowl around the pool, and will incessantly door dig, we leave the sliding glass doors open 6 inches, at least in nice weather.
I had someone walk in the front door of my apartment one day. I had heard the phone ringing inside and hurried in to answer it. I closed the door but didn't lock it. Maybe 15 minutes later, a man (with wife and kid behind) just walked right in. Aparently they got confused and went to the wrong alcove in the building. They were visiting a relative. But it scared me very very very badly since I had been attacked in my home before.
That's one of the reasons that I am as good as I am about locking doors. My neighbor's children would just walk in all the time. So I started locking the doors so they had to knock. I always locked the doors at night but wasn't very good during the day. I figure once your attacked in your own home it's hard to feel safe in your home again.