Originally Posted by themicah

Southwest doesn't have assigned seats. They board according to elite status and checkin time, and people grab whatever seat is open, which ends up being faster than any system with assigned seats tried so far.

If you have assigned seats, however, boarding all-at-once is extremely inefficient. Boarding from the back is better, but is still not optimal. See http://www.wired.com/news/technology/0,70689-0.html