Looks like Brazil will be seeding in Group F

An official bulletin seems to indicate that Brazil will be on top of Group F. This way they will play their group matches at the three biggest stadiums involved in the World Cup (Berlin, Munich and Dortmund).

Germany, as the host, should be seated in Group A. They will play at the same stadiums but in a bit of a different order (Dortmund, Munich and Berlin).

This setup would also mean that if both teams won their group, they could not meet till the final (or third place match). I'm guessing the Germans would like that.

I think this seeding makes sense. These two sides will have the most fans wanting to watch them, so it is only sensible that they go to the biggest stadiums.