For years, I locked my check baggage whenever I flew just to have anyone I traveled with tell me that it didn't matter if I locked my bag or not; if someone wanted to get into it that they would. I really wasn't worried about theft. In my younger days, I always over packed and was afraid that the zipper would move around or part and I'd lose my luggage that way! Not that a lock would have helped that anyway--but it was the mentality of the young!

I bought TSA-approved locks last year. I used them only once. No problems though. I don't pack anything of major value in checked baggages and I no longer overpack, so I just have found it easier not to lock at all.