My house actually nearly got robbed the other day.
I live in the outskirts of London, mainly where all the famous football players live..
One day I was upstairs with my dog and my mum was in her room, when the dog started going crazy..
Anyways, I went downstairs, baseball bat in hand (My dog never goes cray-cray at stuff so I knew something was up) and was shocked to find the back door wide open with the door in the locked position.
Criminals lock the door behind them, while the door is open so they can make a fast get away. Robberies are common in my area (due to the CEO's of massive companies living around here)
There were two laptops on the table by the door, a camera, my mums purse, two PS3's, a 50" TV and a bunch of other stuff located close to the door.
Thankfully, due to my dog being bad ass, none of this was stolen! (the pusillanimous individual must have got scared and ran off!)
tl;dr, get a dog.