I do not think this would always be a big problem. Say you are in 1st class and going somewhere you really did not want to go and it would be fine with you if the meeting or event happened without you.

If it was a business meeting you had to be at your just stuck.

If you are having an anxiety attack and you must get off the plane, I guess you could alway go for the emergency exit. I doubt anyone could stop you if you planned your exit well. Only God can say what would happen once they caught you somewhere on the ground trying to get away!!!!

An attorney might try it to sent up a case to test the detention of people by a public company.

I also ponder the thought of being delayed more than X hours. Is this covered by the cancelled or overbooked flight. Should you not get meal allowance, vouchers for future flight free, etc? The flight is delayed by weather, there excuse, but you could take a bus, train or drive if they did not hold you hostage!