This has happened to me twice. Once on Lauda there was a guy in my seat and for some reason the FAs just would not move the guy. They found me another aisle seat and I got to site next an attractive member of the opposite sex - so all was not lost

Then once on VS this extended American familiy had seats over a couple of rows and decided their assigned seat numbers were really only guidelines, as opposed to any requirement to actually sit there. Needless to say they left me the middle seat - and as you know with VS, this is not good.

The FA talks to them and triumphantly tells me I can have the middle seat in the next row back! (I had an aisle). Took some negotiation to secure another aisle seat...

Not good when the FAs aren't on your side