One thing that stands out to me about tedster's analysis is that there is a VERY real problem of link OVER-DIVERSIFICATION.
We've always heard to get back links from a wide variety of sources. Unfortunately, that is NOT normal. Unless you are proactively getting links, then depending on the site, there is going to be a limited spread in terms of the kinds of sites that are going to link to yours. That is the way it is.
I am sure that there are some sites that will be linked to by news organizations, yet government or educational sites will NOT link to it, and vice versa.
That's my story and I'm sticking to it.