Elvis, I had a rant and a rave about this not that long ago.
On more than one occasion I turned up to check in VERY early (and I'm talking like 6 hours before..........great when you live near the airport
), and have been told on more than one occasion the seats had been reserved or already taken (this has happened with more than one carrier in more than one country). Lo and behold, get on the jet and the punters sitting in emergency exits could be described as a very loose interpretation of able bodied pax. It makes my urine boil.................