I posted the prediction poll here at BYB, and here are the results:
Looks like a majority of voters feel that this series will go at least 6, which makes a lot of sense. These are two very evenly matched teams in terms of pitching, hitting and defense, so I would expect this to be the common thought.
I'm sure that a lot of the Athletics in 6 votes came from some of the members over at Athletics Nation, the awesome SB Nation A's community. It was probably hard for them to not to pick Tigers in 4, I bet.