Seems to me in my research prior to my 2007 trip, I read that you shouldn't put any lock on checked luggage. Maybe TSA "in theory" can open every lock with a key, but apparently that doesn't mean they will. Locking your bag is taking a risk of losing the lock. So I've never locked checked luggage. Now locking it once you reach your destination is another thing. I would assume it is insecure there. Of course, bolt cutters aren't that expensive, so a lock only stops the very unprepared theif. I'd say if it is really valuable, have it on your person or in a safe.