In putting together the bracket, a few very strong contenders rose to the top. As a result, they were given high seeds. Many of the other contenders - while perhaps equally worthy - have not been regularly sampled by the selection committee. As a result, anything seeded below the top 8-12 (roughly) was given a random seeding.
In any case, we have no fear that the best beers will make their way through the bracket. Vote now, and stay tuned.
Thanks to Mike at STLHops.com, who doesn't mind me repeatedly stealing his ideas.