Airlines have inflicted so many annoyances on their customers--intentionally or through incompetence--that it's almost refreshing to read about a situation which wasn't actually caused by the airline.
The story is that a passenger flying business-class internationally with his wife on United Airlines did everything right to make sure he got the seats he wanted: he booked well in advance, got seats together, checked in early, and had super-elite status on United.
As they were boarding, though, the wife was pulled aside and given a new seat assignment so the couple would no longer be seated together. Naturally annoyed, the customer asked for an explanation and was only told that "there are some passengers we can't move."
The flight attendants also seemed confused by the situation, but wouldn't provide any explanation other than "Some passengers we just can't move."
Eventually the passenger took the hint and figured out that (spoiler alert!) the wife's seat had been claimed by an air marshal, and of course the crew isn't supposed to reveal the presence of an air marshal on board. And the couple did manage to arrange a seat swap so they could sit together.
But even though the airline didn't create the situation and wasn't allowed to explain it, it seems that pulling the wife out of the boarding line was about the worst possible way to handle this. At a minimum the gate agent could have paged them before boarding and--without explaining the reason--told them that it was necessary to reseat the wife. Even better, the gate agent could have made some effort to arrange it so they could still sit together.
The lesson, I think, is that even when a company is placed in an unusual and difficult position, there is still a choice about how you want to treat your customers.