Almost every guy who has had the pleasure of living around one or more females has run into the problem that somehow it is the guy's fault when the female falls in when she forgets to put the seat down on the toilet before use. The author shows that the economically most efficient algorithm in most instances is the "selfish" rule where the user of a toilet puts the seat where he or she needs it before use, and then leaves it there afterwords. It is only in the extreme situations where it is more efficient to have either an "always up" or "always down" rule. For example, growing up in a family of six males and one female, it would have been better to have an "up" rule, except that she (my mother) made it clear that that meant that we would have to clean the toilets too. Which changes the situation to one where a "down" rule was preferable. (Actually, being grossed out coming downstairs, she pretty much let us use the "selfish" rule in the bathrooms there, and imposed the "down" rule upstairs in the bathrooms she used).
Nevertheless, this is ammunition for every guy facing the prospect of an irate woman who tries to tell him that it was his fault that she didn't check and fell in in the middle of the night.