A few weeks ago: I was one of the first to board in Y on a UA flight LAX-ORD. About 3/4 of the way through boarding, the woman in the bulkhead row in front of me & across the aisle asks me if I'll switch with her because she doesn't like the bulkhead. Sure, no problem. I get settled in, and put my nose in my magazine. A few minutes later, a straggler arrives, and accuses the woman in the original seat of being in "her seat," demands to see her boarding pass, etc. Minor chaos ensues because her boarding pass was for a different seat, and as I try to calm the woman down, the FA comes over and asks for my boarding pass. She tells me and the bulkhead woman to take our original seats, that she'll straighten it out, and walks away. I knew I had been op-upped, but I played it cool, as these two women were obviously not FF'ers, and I wanted to wait for the FA to "make it official." As I was walking up front, I heard the FA tell the latecomer that there was a woman who was going to ask her to switch seats, but "don't you switch with her if you want to keep this seat."

As I'm gathering my belongings to move up front, the woman who was originally assigned the bulkhead asked out loud why I was bumped up front instead of the latecomer. (Another clue that she was obviously not a FF'er.) Shortly after takeoff, I looked back into Y, and I saw that the original bulkhead woman had convinced somebody else to switch with her.