so here goes my theory on the 12 v 5 upsets that are not so much upsets anymore. The 5 seed tends to be the 3-5 best team in a power conference. Purdue and Baylor are perfect examples. On the flip side, the 12 seed tends to be the very best of the automatic bids (power conferences leaders excluded). The 11 seed is where the bubble teams get seeded. As a result, you really have two very comparable teams playing each other. The very best auto qualifiers can easily keep up with and even beat the 4th best power conference team. It only seems like an upset because the power conference team has been on TV all season long and very few get to see the quality of the Yale's and Little Rocks.
