According to a friend in law enforcement it is a good idea for everyone to keep doors locked. And it also a good idea to look outdoors before opening a door for whatever reason. There was recently a local incident where three teen age punks had been watching an elderly couple and came to know their habits quite well. They knew that shortly after the 10PM news, they would open the door and let their dog out to go to do it's business before going to bed. The lady opened the door and let the dog out, she LOCKED the door and returned to the kitchen to pick up, her husband went into the bedroom and started getting ready for bed. When the lady opened the door to let the dog in the punks also pushed in. One of them hit her in the face, knocking her down, she screamed, her husband came back into the den area to see what the problem was. They beat him severely and tore the house up looking for valuables. Not finding much, and only gaining $45. for their efforts, one of the punks suggested the one with the gun kill them. Luckily they left the house without firing a shot.
Makes little difference who or where you are, someone is probably watching and set to take advantage of you when you place yourself in a venerable position. Just be aware of your surrounds, don't set patterns (habits) that can be use against you, and try to secure your home by using lights, bushes that have stickers (so they won't hid in them), keep your gun handy, and pray for them AFTER you have eliminated the threat.