The Superconference Armageddon feels more inevitable than ever these days, with one potential outcome of the Big 12's dissolution being the formation of four or five 16-team conferences. We've had conferences larger than 12 members in major college football before, so can they tell us anything about what could be in store if those big leagues do come to fruition?
Southern Intercollegiate Athletic Association
It formed in 1894 with seven members, and it doubled in size in 1896. It didn't really function like the conferences we have today do, as dozens of members came and went over the years. It was never stable as a result, and it ended up giving birth to both the Southern Conference when dissatisfied members left in a large bloc.
In 1921, 14 members left after the SIAA failed to pass rules banning freshman participation and paid summer baseball. The following year saw six more schools join, and it got up to 23 members from 1928-32.
In 1952, the largest seven of the 17 members chose to leave to create the ACC. One of their primary concerns was the SoCon's ban on postseason play.
The league started with 13 members, as noted above. Sewanee left in 1940, and Georgia Tech and Tulane left in the 1960s to become charter members of the Metro Conference. As we all know, the league expanded back to 12 in 1991 and hopes to get back to its original 13 next year.
Western Athletic Conference
The conference started out small, and got smaller when the Arizona schools went to the Pac-10, but it gradually got bigger. Then in 1996, it jumped from 10 teams to 16. It put them in a pod system of four groups of four. The experiment lasted just three years. Concerned with being associated with lesser academic institutions and paying for high travel costs, eight schools broke off to form the Mountain West Conference.
Membership has changed considerably over time, and just one charter member (Ohio) is left from its inception in 1946. It expanded to 12 with Marshall in 1995, to 13 with Buffalo in 1999, and to 14 with UCF in 2002. Marshall and UCF left in 2005 to join Conference USA, bringing it back down to 12. It added Temple in 2007 after the Big East kicked it out, and it is adding brand new I-A school UMass in 2012 to return to 14 teams.
All conferences that went over 12 members had some kind of instability to them. We know that because as of today, only the MAC is above 12 members among I-A conferences.
The first two conferences listed don't apply much to today, as disagreements over fundamental rules like whether freshman can play have been rendered obsolete by the standardized NCAA rulebook. The SEC's original fall from 13 down to 12 isn't applicable either, as no one I know of on the I-A level is considering de-emphasizing athletics altogether. The 14-team MAC was a victim of being low in the conference pecking order, but the major superconferences, once formed, won't feel similar pressures (and it made it back up to 14 anyway).
It's not for nothing that skeptics point to the WAC's experiment at 16 members as a cautionary tale for future superconferences, and it is well worth it to learn from that league's downfall. I'd bet the conference most in danger of repeating that bit of history is the hypothesized Pac-16, which would undergo significant culture shock, incur large travel costs, and have a highly stratified structure in terms of academics. The Big Ten could also end up there depending on who it chooses for schools 13-16.
It's easy to look at conferences purely through the lens of I-A football as it stands today and not pay attention to how things are on other levels and in other sports. The 14-team Atlantic 10 is worse at math than the 12-team Big Ten is. Big East basketball has 16 schools and is going to 17 next year with the addition of TCU. Division II football has three different conferences above 12 members.
Of course, I-A football is seen as a whole different animal because it is a whole different animal. The instability going on right now is based on schools looking to maximize TV money. We might end up with four 16-team superconferences, but there's no guarantee that they will be the optimal setup for maximizing TV money. If they're not (and I suspect they're not), then we'll see some of the more ruthless big fish try to leave behind the smaller ones in smaller conferences.
Schools changing conference affiliation has been the rule, not the exception, for as long as college athletics have been organized. I see no reason why a superconference system has to be the final configuration any more than the six conference BCS system has turned out to be a permanent fixture.