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I think USC is definitely above 1/4, probably about 1/3-1/2, but in general I think you're right. They're not >1/2 in my opinion.

Here's a good look: https://www.nytimes.com/interactive/2014/10/03/upshot/ncaa-football-map.html#9,33.588,-117.041
It gives you the top three by zip code. In the bulk of LA County, USC dominates with anywhere between 33-50% of fans, with UCLA in second at around 20% and Oregon in third at just under 10% generally. Get a bit farther south, such as where I live in OC, and USC drops to about 20%, still followed by UCLA and Oregon. But that shows you that the "local" passion dwindles and there must be a lot of transplant support.

Thank you for the map link.  I couldn't get the link in the original NYT story to work.  
Just one semantic point of clarification.  I don't consider USC's 33-50% to be indicative of USC "dominating".  I admit that it is my definition not webster's but to me, dominating is two things:

• Being the favorite team of more than half of the people in a given zip (51%+)
• Having no other team within one-third of your own.  

Ie, if you found some zip in Michigan where Michigan had 51% and Michigan State had 49% that wouldn't be "dominated" by Michigan because it is too close.  Similarly in some of those SoCal zips where USC has 30%, UCLA has 8%, and Oregon has 7% I don't consider that to be dominated by USC because they aren't half.  

When I think of "dominated" I think of something like the Omaha Metro Area that the article used as an example where nearly three quarters of CFB fans are fans of one team, Nebraska.  

https://frankthetank.me/2018/05/18/oh-the-places-youll-go-where-big-ten-graduates-live-and-conference-realignment/

Frank the tank posted some interesting stats on where BIG graduates go....     Basically every big schools sends kids to LA after graduation.   Same with D.C.,  SF and NY.  Kids from all the BIG schools end up in those cities post graduation.   I'd guess other conferences would see something similar.    Some cities have a lot of college fans, but just no dominant market team.  

I think that @bwarbiany and @Entropy are right.  Certain cities (NYC, CHI, LA, ATL, SF, DC, etc) are "magnet" cities so they are inherently going to have a mix of fans of pretty much every major CFB team and the home teams will never really "dominate" (when defining dominate as I did above).  

Consequently, none of those media markets can truly be "dominated" by any one team or in some cases even any one conference.  I would imagine that the SEC collectively dominates ATL and that the B1G collectively dominates Chicago.  

Agreed. Which is almost why it's more interesting to look at the major metropolitan areas as far as "outliers" are concerned...
LA for example is a lot more USC-centric than, say, Chicago or NYC or San Francisco. It's about as USC-centric as Atlanta is UGA-centric. For a small, elite, private school, that's surprising. It's not like Chicago rallied around Northwestern in the same way that LA has rallied around USC. 
What's kinda interesting is that I looked at the SF bay area, as I'd lived there in the past. In San Jose, SJSU is the leader, but in only a few zip codes do they get above 20%. In SF itself, it's the same as Chicago or NYC, with basically no team having a clear >10% lead. But oddly, on the peninsula, Stanford is really popular in a way that surprised me. The zip codes near Palo Alto have a 35% plus Stanford support, some >40%. But even as you get progressively farther away, there are a lot of areas that Stanford is still >20%. 
With all the transplants to the Bay Area, PARTICULARLY the number of highly educated [i.e. college grad] transplants who bring their own rooting interests, I'm surprised that Stanford, as a small elite private school, has that much support. 
That one kinda surprised me. Seattle was a little bit surprising as well, with how much it's grown over the past two decades, and how many transplants they have--again, highly educated transplants drawn in by Boeing, Microsoft, Amazon, and all the tech companies that have sprouted up from those big ones. It's basically dominated [to use your term AND definition, medina] by Washington support. I thought it might be diluted more than it has been. 

Agreed. Which is almost why it's more interesting to look at the major metropolitan areas as far as "outliers" are concerned...
LA for example is a lot more USC-centric than, say, Chicago or NYC or San Francisco. It's about as USC-centric as Atlanta is UGA-centric. For a small, elite, private school, that's surprising. It's not like Chicago rallied around Northwestern in the same way that LA has rallied around USC.

I'm guessing if NU performed on the gridiron the way the Trojan War machine has for over 100 yrs Chi-Town would have.Of course LA didn't have a pro team until the Rams arrived in 1946 after winning a championship I believe

I'm guessing if NU performed on the gridiron the way the Trojan War machine has for over 100 yrs Chi-Town would have.Of course LA didn't have a pro team until the Rams arrived in 1946 after winning a championship I believe

I was thinking the same thing.  In deference to the late Marcel/nuwildcat, Northwestern's long-term performance simply pales in comparison to USC's.  If Northwestern had a history like USC's, then I would assume that Chicago would be much more strongly supportive.  

Is there some viable known mechanism by which the B1G can eject a university?

Yes. The conference discussed a Penn State whack a few years ago (Sandusky).

I think it is by unanimous vote of the other 13 members now (at the time of PSU it was 11 members). 



Not easy to do. PSU never got to a vote - only discussion.