all about money - market size, alumni size, TV eyeballs, brand equity, etc. If you assume that the SEC responds to the B1G by raiding the ACC's top schools, so now ACC schools are available to the Big12, then you have to ask yourself...how does Utah stack up (from a money standpoint) against the following?
Miami (if Super2 don't grab)
North Carolina (if Super2 don't grab)
Virginia (if Super2 don't grab)
Virginia Tech
Pitt
Louisville
Georgia Tech
or even the competition in their own current conference...
ASU
Colorado
Arizona
You have to figure that the Big12 can't add an infinite number of teams. There is a limit somewhere, so I would not be so comfortable if I were a Utah fan - especially considering they share a market with a current Big12 team.