What's your feelings about seat policies regarding fat people on airplanes?

It comes up in the news every once in a while about airlines harassing overweight passengers or requiring them to purchase multiple seats.
Recently director Kevin Smith was booted from a Southwest flight, and there have been many other people who have been booted or required to buy a second seat too.
What’s your feelings about this and all the issues pertaining to it? I have mixed feelings so I’m interested in hearing all sides.