Southwest airlines policy

[rswall]

While on two separate flights- both coast to coast- I've been stuck sitting between/beside two other very obese people. One one flight while sitting between the people- their upper bodies/arms "spilled" over into my seat- squishing me and every time I moved- I "disrupted" them and they got agitated with me. I was supposed to have the aisle seat, but they both couldn't fit next to each other in the middle and window seats, so the flight attendant asked if I would sit in between them- so rather than being uncomfortable on just one side- I was uncomfortable on both.
Yes, I think it's fair to charge overly obese people for two seats if their size causes them to infringe on another person's ability for a comfortable flight. I'm 5'5" and weigh 115lbs. and fit very comfortably in a coach seat- why should I have to pay more to upgrade to business or first class- let the "larger" person do that- the price would be the same as paying for two seats and they would be more comfortable.
This isn't a new concept- airlines have had this policy for years- and it was the job of the travel agents to enforce it, however, now that people are able to book flights on their own- there is no way to "police" whether someone would need two seats.
I don't think the practice is discriminatory- as I said- why should I be uncomfortable because I have to sit next to an overweight person who takes up part of my "designated" space?