To Capot and F3G who have asked some interesting hypothetical questions. I also am a Number 1 for a free-seating company and if a full flight has one seat down (taken up by lard), after consulting the captain, we would probably follow the same procedure if one seat was inoperative for another reason (such as vomit/pee or broken). That is call for volunteers (including speaking privately and respectfully to the fatso to encourage him/her to volunteer first) to take the next available flight, offering increasing amounts of cash incentives until the cash incentive reaches the value of compulsory compensation. (Similar to an overbooked flight). If still no volunteers, the last to check in gets offloaded and we're on our way. If the situation gets out of hand (ie aggressive/abusive) then police are called. Offloading someone who doesn't want to be offloaded can be difficult hence the volunteer method is preferred. Although the Captain does have the last word, in my experience, any problem relating to the cabin they say "what do you want to do about it" or even "I'll leave it in your capable hands - if you're happy I'm happy".