LOL.
This is actually a common belief--sorry to say, gsmooth, you are not one of the few geniuses who understands this--but it is a myth.
Sports books absolutely take positions on the games, and they are on the right side most of the time. It is part of their strategy. Simply taking the vig on an evenly distributed bet does not make money fast enough for them.
You want proof? Think of the proposition bets. In 2006 you could get 10 to 1 odds on Tiger Woods winning all 4 majors. A horrible price, but here's the thing: you COULD NOT TAKE THE OTHER SIDE OF THAT BET. The books were taking a position that Tiger would not win all 4, at a price very favorable for them.
I promise they do the same thing on the money line, and the spread, and the over/under, and everything else.
Of course they would like you all to believe they are just taking rent on the bets, but in truth they are betting against the public. And mostly winning.