I know most of you already are aware of this, the info could be usefull for folks who are not in the US or Canada.
We just found out the hard way that it is not a good idea to lock suitcases. We have (had) the old type of suitcase not soft sided, and they could pop open unless the handle was locked. Homeland security can and will open any bag at random, ours was one of them. They do tape it back together again with duct tape however the case is wrecked. We now have a new set of bags with TSA approved locks they can open with their code. Strange the case they opened was full of clothes heading for the laundry.
I know now this is also the practice in the UK and all airports I guess, we all want to be safe. Here are a couple of links;