The thing we can give Callahan credit for is he proved Nebraska could bring in a highly ranked recruiting class. Obviously he had more weight to throw around as a former NFL head coach, but it can still be done.
Furthermore, I think location matters some, but let's take a look at other places that I personally believe aren't the most lucrative of locations, and schools in these cities have won BCS games or competed for titles in the last decade - Ann Arbor, Mich., Columbus, Ohio, South Bend, Ind. and Eugene, Ore. Quality matters over quantity here. These places aren't in warm weather, they're not by some snazzy beach and there are far better places to spend your summers.
These places, though, have had better coaches and talent in place more recently that Nebraska. But, as I've opined the last couple of days, Nebraska has talent here capable of competing for conference titles, and has had it. Talent aside, there's little arguing against the idea that we have coaching deficiencies somewhere.