Philippines. I had been gone for 3 weeks and just wanted to get home. I ended up getting stuck in the middle seat. The passenger in the window seat was so large that the whole flight their derrière and legs were impinging my space. yes, I was irritated. Yes, I also know that some people can't help it. I am assuming that this was not the case with this passenger as they polished off a full size bag of Chex mix on an hour and a half flight, which only increased my irritation. So my answer is, absolutely, they should be required to purchase two tickets. Especially when your lack of effort affects my comfort after traveling for almost 24 hours.