I've always thought that home teams hold a big advantage in Saturday games, because that's when the biggest crowds show up and the home team doesn't want to disappoint their fan base.
Brings me to an interesting stat. Through the first 6 weeks of the season so far, the home team is 50-40 in Saturday games. But here's the weird part: in the NL, home teams dominate on Saturday (31-17), while in the AL the home teams are losers overall (19-23). I guess it has something to do with the DH.