There was a considerable hoo haa on my last flight EWR - LHR last Friday/Saturday. There had been a plane change to a 777-200 from another 777 variant. This meant there were a different arrangement of seats and several passengers who had selected and purchased exit seats were left in their original seat numbers but these were no longer exit seats. I had noticed at 24hr the aircraft change and was able to reselect an exit seat but it seems I was the only one to notice and make a change.
There was a considerable fuss made by to understandably upset folks who had paid for the seats and quite an awkward moment as a couple of passengers refused to move from the seats they though they should have had. The poor CC were put in a difficult position and the another more senior staff member was spectacularly un-sympathetic just saying it was what it was and they would have to move.
Thanks were due to a young lady who agreed to move from the exit row to allow the family with a small child and a baby to take over that row with the bassinets but it seems extraordinary that the checking folks did not advise passengers as they checked in that there had been a seating change and avoided putting the CC on line like this.