Continental Airlines -- Fat Person Policy ("Passenger Of Size")

[Shakes]

Continental Airlines, like almost all airlines, has a "passenger of size" policy, where the passenger is required, at some unknown threshold of size, to purchase an extra seat in order to travel.

I'm curious as to whether anybody here has any experience with this policy and how it is enforced.

In particular,

Is there some definite way to determine if you are fat enough to fall under this policy?

Does it matter if the plane is full (i.e., will they not force the extra seat on you if there are several other empty seats on the plane)?

I didn't fall under this policy the last time I flew to Vegas, but I didn't bring it to their attention either. The plane was not full and did have several empty seats, so maybe it didn't matter.

I talked to Continental's customer service and they weren't helpful with the policy. They couldn't clarify whether it mattered if the plane was full.