Why would anybody spend money to try locking their suitcase, when the TSA has the right, and may as well do open your bag for inspection, or when it's so easy for any airport worker to find a way to open your bag?

As mentioned above (it took quite a few posts till finally someone mentioned it), I don't keep anything valuable in my checked-in bags, and all I do is lock them with a cheap plastic cable-tie, I bought a whole pack of them. That way, when my bag arrives from a flight I can immediately see if it was ever opened, be it by the TSA or someone else, doesn't matter... if the cable-tie is there, I have no worry. Simple.

I just flew from London Heathrow to MSP and lost some things to TSA despite a lock. They had left a note in the bag but it was interesting that they only took all four of my red metal water bottles (with original tags on them and empty) that had a British crown and the saying "BE CALM AND HAVE A DRINK"!on the front of the bottles-very cute!
I had a very long telephone chat with the supervisor of the TSA up in MSP airport . He told me that they video tape every search of the bags and that he would go back and replay the tape. He called back several days later and said that nothing was taken so it must have been back in London?
After telling him that I work for the airlines,had a crew tag on the bag along with a standby bag tag and that the bag is not put on to the very last minute I was kinda thinking that the TSA did it while they had my bag for almost two hours in MSP.He told me that I must be mistaken and how could I suggest this.
I then went into the number of passengers I have had through the years that end up losing one shoe from a search;candy or jewelry gifts taken,etc. Amazing that they know exactly what to take? He wanted me to retract my three letters that I had written to the head of the agency but I won't budge.

It's unfortunate when stuff gets stolen from checked luggage, by whoever gets into the bags behind the scenes.

Point is a lock on your suitcase is not going to stop this from happening, TSA or otherwise. It's a false sense of security imo to even bother using them.

I use either twist ties or a luggage strap to secure my one checked bag, but that's to prevent my dirty clothes from ending up spilled out on a baggage carousel, not because I think I am preventing a thief from stealing my stuff.

This is my experience:

I always lock my luggage from my departure city in Europe or Asia. Once I arrive at my port of entry, I would take out the lock after retrieving my luggage from the carousel and re-check my unlocked luggage. Only within the US did I have items missing...not expensive ones...but still annoying. I'm pretty sure the unlocked luggage becomes more tempting to those thieves.

Why anyone would put anything else except for shirts,socks and underwear into checked luggage is beyond me!!!!!

JoyC, a suitcase, especially the soft one, is so easy to open, that a lock makes very little impression on any dishonest airport worker.... You could as well say that a lock makes one suspect there's some valuable stuff in that suitcase...

......anyone can get into a bag with a nylon zipper with a ballpoint pen, then reclose the (self-mending) zipper with no one the wiser.......

This is frequently posted and it is easily defeated by immobilizing the zipper bodies so the zippers cannot be moved to close it They can get it open with a ballpoint but cannot close it.

fmpden: how does one immobilize "he zipper bodies so the zippers cannot be moved to close it?"

My last three vacations I had TSA locks cut off our suitcases. From now on I'm using a plastic tie.

Easily. We use long plastic wire ties. Put all of the zippers in the same area and lace them together and maybe the handle depending on the bags. All of our rolling bags have a cross zipper for a pouch on top while the body zipper run around the bag. We tie these zippers to the cross zipper. That way none of the zipper bodies can move more than inch or so. You can still pop the zipper with a screwdriver but you cannot reclose it with out cutting the tie. The second advantage to this approach is if the zippers were popped, the lid of the suitcase is tied down on one side so access would be limited to reaching in for either end.