I didn't think about it until I read this article, but...
I haven't heard anyone talking about expanding the playoff field this year. I'm not so sure now, but before, I was in favor of a 6-team playoff with byes for the top 2. I think this might be what Brian advocated also. I always thought 8 was too much. With 6, you could have all the Power 5 conference champs and 1 more team that was a runner-up or an independent or even a non-Power 5 champ.
The author here makes some good points in favor of keeping it at 4 teams.
"Check out the rankings: Iowa is No. 5, followed by Stanford, Ohio State and Notre Dame. If you included all these teams, you would have effectively rendered the Big Ten title game irrelevant. And Michigan State's stunning victory in Columbus. And Notre Dame's loss to Stanford.
And you'd still have No. 9 Florida State and No. 10 North Carolina, two-loss teams just like Notre Dame, howling over perceived injustice."
With the 4-team playoff, the regular season is just as important, and even more interesting, because with just a couple games to go, seemingly everyone in the top 15 had a chance to get into the playoff if things fell their way. And I think it's at least as fair as any other system would be. 2 teams is too strict. 8 teams lets in too many teams who just don't have resumes that compare to the top teams.
At some point the toll taken playing more and more games does add up, but in terms of the enjoyment and fairness of the sport itself, a 6-team playoff still may be best. Having said that, do you really think Iowa should be in there? I don't. And that would have taken away from the B1G championship game since it would have just been for seeding. I would like to see Stanford in there though; I can't say they're a step down from the current playoff field or undeserving. I also think 6 would have been better last year. There was definitely a good case for TCU or Baylor.