Shaddows, that makes alot of sense to me and ties into what I see competition wise. When we started we had a couple competitors, now we have hundreds if not thousands.
I havent found any tie in with page count, same with my competitors which I have tracked for a decade. Page count triples in the primary results or falls by as much and nothing changes.
We really havent optimized our pages in years. We focus more on the content and have stuck with our basic vanilla SEO.
Our backlink profile is pretty diverse and I think we only have gotten 3 of the hundreds of thousands of ibl's ourself. Those being yahoo, botw and business.com. All of our content is handwritten. Links are all over the place. Links range in strength from colleges, govt, fortune 100-500 companies down to smb and personal websites. So many links infact I don't know the true number. Some with natural anchor, some with just the site name.
We started out as a hobby in 98. Over 50% of our visitors come direct. That number has continued to grow since 98 and that's the number I care about the most. No doubt about it though, Google was a big part of our success. I cant imagine what they have to deal with.
We have set ourselves apart from our competition in many ways which is why we have become a brand name now. That hasnt seemed to make a difference so we can rule that out.
Are we an authority? A true authority? Hard to say really, what is a true authority? We have been around for a long time, we have hundreds of thousands of natural links. We rock on social networking sites with legions of fans. We are quoted by wikipedia, referenced by govts and schools, featured in companies advertising and we have dozens of people bidding on words related to our name in adwords.
At the end of the day Google has to look after it's own interests and I can respect that. I am grateful for whatever they deem we should get and have resigned myself to traffic growth from other channels which has become a much more productive use of my time. The ceiling/throttling is real for some sites but I cant see any way around it.