Several people have mentioned to me that all of the American League teams are ahead of all of the national league teams, or vice versa (it changes from one day to the next).  The reason for this is very simple: until Interleague play begins, there is no way to know which league is stronger, and by how much.  So it's completely random as to whether a National League team is ahead of an AL team.  The rankings are (for now) only useful in comparing teams in each league.