I did an airside transit through IST on to BA to LHR a few days ago. Since I didn't visit the check-in desk, I had to check it in at the gate. It was somewhat similar to the other encounter, however after showing that I had a laptop I was told to sit down with it and then check it in with the airline when they were ready.
After 15 mins, I was approached and told that to go and check in my bag. I went to the desk and was asked to sit down behind the desks for a few minutes. The BA agent then approached me and asked me to put the laptop in my check-in bag, and left me to get the luggage tag. At the point I could quite easily have just put the laptop back in my backpack and carried it on board and they would have been none the wiser.
Someone took my bag until the end of the jet-way and left it there for a luggage handler to take to the hold. When I passed it, I could easily have just picked it up and took it on board with me again.
I was in transit to the US so asked for the bag to be short-checked to LHR where I picked it up and carried it on again for my next flight.
Seemed to be a process completely full of holes.