Sebastian commented to let me know that Matt Cutts of Google has confirmed at Sphinn that whatever was causing quality sites to be moved down to the 6th position in the Google search results, is now being reversed. Matt said:
When Barry asked me about "position 6" in late December, I said that I didn't know of anything that would cause that. But about a week or so after that, my attention was brought to something that could exhibit that behavior. We're in the process of changing the behavior; I think the change is live at some datacenters already and will be live at most data centers in the next few weeks.
In general if you think a site might have a penalty (perhaps from past behavior) and you think the site is clean presently, you can do a reconsideration request in our webmaster console to ask Google to take another look at the site.
I just love it when the SEO community's communication helps Google notice these things and make changes based on our feedback. I should really go back and document each and every time Google has made changes based on SEO community feedback.
In any event, if you were impacted by this penalty - you don't have to do anything, as I thought. Just wait it out and Google should take care of the issue on their side.