Interesting. I, too, took a step back to assess the quality of my site vs my peers and found a few things. There are takeaways to this event. First, it tells me that my overall position is not deserved based on certain factors. This algo is about quality and whether you are answering the needs of users.
I'm guessing that large authority sites are upheld to a certain standard that's different from smaller sites. My authority site has much much better content than my smaller sites, but this is also the site I learned on, vs the smaller sites I run that I built when I had more experience.
The difference is that my authority site tends to be more "quirky" while my smaller sites are more commercial, maybe even more dry. It would be a shame if I had to change my style because of such an update. But there could be other factors too. The quirkiness made me stray from usefulness, perhaps. I saw that my older pages had a lot more "musings" and rambling that were on the shallow side, vs more useful, informational material. Should I be penalized for that?
I also monetize my authority site a little harder as it attracts more ads, but the difference between this and my smaller sites is negligible, in terms of ad density or layout.
I can also see that this is a message that says, "well if you are an authority site, you better deserve it". That may ring true. I certainly question whether the algo should have penalized the big site for being interesting/different/quirky vs less useful in some areas as opposed to my more boring/straightforward/on-topic pages on my smaller sites that are now booming in traffic.
I would love to know what it is they are looking for. I am sure I've tripped some of their quality factors somehow, and maybe SIZE is one of them. Smaller sites that are just as quirky are not penalized. Smaller sites with more ads are not penalized. So really, what is it? The bigger you get, the more important you get, does that mean we have to act like the other big guys too and be much more "pro" about things? Or I suppose, one way to look at it is that we are "whittled" down to size and now simply reflect the traffic we deserve to get...