I wanted to put my fridge in my camper but I needed to run generators or external battery, so its in the car with the dual battery system. On longer base camp trips I do supplement the batteries with a generator but I try to limit the use due to noise. The only problem I've had with the fridge in the car is when my second battery lost a cell (bad battery mangagement) and the fridge wouldnt cool down properly. As for theft I have a patrol wagon and its locked at night and when we go on walks. I havent really come accross theft while camping, but its always on the back of my mind.
Always remember that your not the last person to visit, be a responsible camper to insure future generations get to see.