I got sort of seat poached on an AF 747, CDG-BOS a few years ago. Back before my savvy traveler days, I waited until the airport to try to get a better seat in Y. Turned out there was one middle left on the upper deck, first row. I arrived at my seat to find that the aisle seat was open. A french couple had originally been seated in the aisle and window, but the husband took the middle so he could sit next to his wife.
Needless to say, I did not complain.