I went through screening one day and forgot some change in my pocket. I went through the body scanner and realized it, so I reached in my pocket to get it to show the screener but it was still in my fist as his device showed it, but he basically just wanded me over the pocket my change had been in and sent me on my way. I never had the chance to show him that I had it in my hand now and he didn't ask nor did he find it. Can you imagine is someone had even simple sleight-of-hand skills?I've had some personal experiences of my own over the years, mainly involving my pocket knife. I have a lifetime habit of carrying a small folding pocket knife with me at all times, and many is the time that I've forgotten to remove it (post-9/11) before flying. Only once was that pocket knife detected by airport security – and that was in London, getting ready to come back to the U.S. They confiscated it and mailed it to me (I paid the postage). I never counted the number of flights inside the U.S. where I took the knife through security, but it has to be in the range of four or five dozen times.
Most of the news stories about the current brouhaha don't mention it, but TSA (and its predecessors) have been failing these spot checks for years. In fact, they've never passed one! As Bruce Schneier likes to say, the TSA is all about security theater. It doesn't actually provide security, just the minimum necessary appearance (for sheeple pacification and political purposes) of it.
The continually failed security spot checks reminds me of a similar experience I had in the U.S. Navy. Hopefully they've gotten better by now, though I wouldn't bet any money on it. I served on a nuclear-powered ship that carried nuclear weapons, and it was a ship that could serve as “flag”, meaning that it could carry an admiral and his retinue – and had extensive secure communications facilities.