Everytime I've checked a board bag since 9/11, as well as friends, TSA has opened it up for inspection. They leave you a little paper tag inside to let you know they did so. Not a big deal so far, since everything has been in the same place I put it originally.
Locking your checked luggage is pointless imo. If you use a random lock, they'll just break it to get inside. Even if you use a TSA approved lock, from what I've heard, they usually don't know or care and end up breaking it anyways.
As far as the accuracy of my list, feel free to let me know if anything is incorrect, but make sure you know what you're talking about. I updated all the info. the day I posted it up, so it's current.