The seats pop up for maximum sardine-can factor during rush hour. Sounds like a great idea to me. I hate sitting down on the subway in general and especially when the cars are crowded. Less Eau de Ass when standing.

http://www.nydailynews.com/ny_local/2008/12/08/2008-12-08_seatless_subway_cars_debut_in_boston_and.html