Do you get double frequent flyer miles?
As mentioned before all the airlines have this policy in their books, southwest is the only one with the guts to put it out in public and use it. I would think that they have had their lawyers go over the actual policy with a finetooth comb before they release it to the public like their did and it is a poor job done by the reporters explaining the policy because they wanted to make it into a bigger news story then it really was.
I agree with the policy. I have paid for my seat and it is mine for the duration of the flight. I have ended up next to people twice who just put up the arm rest and used up my seat. Luckly I was able to be reseated once but the other time I had to endure an uncomfortable flight.
I have been on smaller airplanes that weight you and your luggage before you get on the plane to get the weight distribution correct. The check-in agent could care less about how much you weigh. It's not like they are going to insult you to your face.