It was very obvious on the broadcast last night - as I flipped between our game and theirs and then watching OT it was very obvious there were large chunks of open seats in the endzone and upper deck of the sidelines. Still a huge draw of number of fans compared to us even on our best game this year WITH cheap tickets. I will say that Thanksgiving weekend likely played a part in it for yesterday, but I wouldn't be surprised to hear that many people lost faith in their program after the EPIC scandal that took place last year.
That being said, I've noticed student section turnout at many schools has been rough this year - witnessing it firsthand at Iowa, paying attention to Wisconsin, PSU, MSU, and a few others on TV. I think that winning or having a certain atmosphere is not enough and I'm not sure what athletic departments can do if teams like Wisconsin and all their gameday traditions, 45k student body, and 2 recent Rose Bowls can't fill the student section at kickoff or even by halftime. MSU has had quite a few good seasons recently (winning 4 straight against Michigan even) and came in to the season ranked in the top 10. Lost their 6 games by 13 total points. Yet against ranked Nebraska their student section wasa little over half-full. I think there's a tough road ahead if your school is not named Michigan, Ohio State, or Nebraska in that students may only feel the desire to show up if the game is against a highly ranked opponent (not necessarily just a rival), your team has won most or all of their games, and the time of the game is right (night games are best, 2:30 starts haven't shown on TV to be any better than 11 AM starts as far as students go).
As for regular season ticket holders, I may sound a little lame here, but I do think there are many people out there (in general, not just MN) who don't have the funds to afford tickets and gameday expenses like they did prior to the downturn. I don't think it's a coincidence that PSU's numbers were high through 2008 and then began dropping (2008 they went to the Rose Bowl, 2009 they still went 11-2, it's not as if the team wasn't winning). Tickets, fees, parking, concessions, travel is all expensive, especially for schools like PSU where their fans mostly don't reside in the area. I don't really know what the other issues are affecting attendance, but I suspect increased TV coverage and quality of games broadcast, the ability to watch many games basically at once, rewind/pause live TV, ACTUALLY see replays rather than being left in the dark, has all contributed to people deciding to just stay at home. Perhaps there's a difference in priorities for people (generational? geographic?) making them care less about football or at least attending football games.
Whatever the case, I think the U has a VERY tough road ahead as far as attendance goes if schools like MSU with good recent track record and PSU with all their history and tradition can't fill their stadiums... Ticket prices, atmosphere, winning won't be enough, clearly.
