Originally Posted by OskiBear

On Southwest, there's a process known as "Unite the Couple" where they select the window and aisle seat. If you can guess they are a couple, you take the middle seat and call their bluff, forcing one into the middle.
(search for the term on the Southwest board and there are loads of threads about it - unite the couple success, failure, un-unite the couple, ect)

Of course, they could be utterly content to sit apart