I'm "new" to Flyertalk, but I have lurked for years.
The last 3 times that I flew in the US, I ended losing a TSA combination lock each time. I presume that TSA doesn't really like those locks. From now on, I'll probably just use zip ties.
Being in Canada, it took me a while to figure out that TSA apparently considers luggage without locks to be more "secure" than luggage with locks.....!