I forgot to mention my husband’s hypothesis: crowding flights into popular time slots will increase the popularity of building an additional runway at O’Hare, a proposal that has been extremely controversial as it would involve the paving of substantial portions of a couple of nearby towns.
UPDATE: Gary Leff has a post that builds on my earlier post on time slot pricing. Gary pushes the argument in the right direction, and cites some news and research relevant to the question.