Sometimes people forget and sometimes it's other passengers. But TSA procedures make both options more likely.

When you're juggling BP/ID, retrieving your shoes, Kip Zip, laptop, coat, carry-on bag, keys/coins/wallet/watch, and trying to put it all back together, while being yelled at to move along, it's easy to forget something or for someone to (accidentally/purposefully) take your stuff.

Last time through LAX the screener grabbed my handbag, with a digital camera, Palm computer, mobile phone and jewelry in it (as well as, you know, a wallet and credit cards) as it came out of the x-ray and said "need to send this through again." At least, I think that's what he said because he was walking away with it at the time. I had to keep an eye on him and collect my other stuff at the same time.

When you're getting a secondary and your bins are at the far end of the rollers, it's easy for someone to grab things. Another time through LAX (boy, I hate that airport!) Mr Radioman and I both got secondaries; when I finished first I picked up his wallet, watch and keys from the bin. No one questioned me or even noticed.

Here in Aus for domestic flights, I take the laptop out. No stupid sock hop, no stupid liquids baggies, my coat can stay on. On the other side, I pick up laptop, bag and purse, put the first in the second, and I'm off. Seems to be as successful as TSA's policies in preventing an attack....