Guesstimations: Super Bowl XLVII - Predictions

I wonder how casinos creates the odds to sports games. This year for the Super Bowl, the most popular spread is the San Francisco 49ers 4.5 points over Baltimore Ravens. Points prediction seems pretty high with at least 5 touchdowns between both teams.

It would have been nice to collect some of the season data to create a more scientific prediction myself.  But just from watching the last two games, my gut guess would be Ravens, 24-21.

Recommended:
http://douglastclee.blogspot.com/2013/02/guesstimations-super-bowl-xlvii.html