I've been thinking about the original topic. The airline's position seems to be that those of us who are large make the trip uncomfortable for others. So I started to think about people who bring children less than two on flights for free, assuming there will be seats for them. If the flight is full, then the accompanying adult must hold the child on his or her lap for the entire flight. If you have ever sat next to one of these parents and child combinations, you know it can be miserable. The kid flops around into your space. Every move made effects you. I've been kicked and punched. If the airline stopped offering free seats and made the parents pay, I'd think the two seat thing for overweight people was fair. Why should those with small children get a discount for making me uncomfortable, while I might be expected to pay extra for the same offence?
My other question is about enforcement. If I pay for two seats then they are mine. So, if I'm sitting there in my window/center double seat, and the person on the aisle sees it as an empty seat and starts putting stuff on it, or raises the arm and slides over a bit, or uses the underseat storage, can I tell them no? And will the flight attendants then have to arbitrate if the person doesn't comply. I'll expect double everything, of course. Double checked bag allowance, double weight allowance, two meals, double drinks, two blankets on the airlines that still supply them, and double frequent flyer miles.