Extra leg room seats with continental?

I just checked in for a Continental flight and I had the option to purchase an extra leg room seat; actually that was the only option I had aside from staying in my pre-assigned seat. Every seat in my row is extra leg room and so are the seats in front of and behind me. Since about half the seats were available and all of them carried at least a $39 fee does that mean this isn't actually about extra leg room? I mean how can every seat on the plane be extra leg room? Is this just a crafty way of charging for changing seats? Or is there some justification for most seats being extra leg room?