robdwoods - 7:15 pm on Apr 5, 2012 (gmt 0)
Looking at a few of the pages where we are seeing a drop in direct long tail traffic from Google, it's obvious to me that the internal anchor text has been discounted, as well as some kind of optimization de-ranking. (or a combination of both)
Formerly top ranked (1-3 serp rank, longtail) internal pages such as [brand widget model] that were linked only internally are no longer ranking in the top 20.
I'm seeing some of the same on one site I analyze (not my own). There looks to be a big discounting of internal anchor text but also an adjustment for over-optimized anchor text, especially to deeper pages.
If this persists I'm not sure of the solution beyond encouraging more varied anchors to those pages (something that really should have been on SEOs' radar for some time).