Rasputin - 4:04 am on May 27, 2013 (gmt 0)
Just to share my own experience in case it helps gain an understanding of penguin. Our main site lost about 20% traffic with penguin 2, and has had absolutely no active link building effort for about three or four years, the entire focus being on making the site better for users.
Several years ago we did some (small scale compared with many sites) directory submissions and article submissions when they were 'popular' and I have never made any effort to remove old links from these or get them removed.
I also never accept 3rd party articles containing links and only occasionally include links in our own articles, and make no effort to use particular keywords in any article. There are no link exchanges on the site.
So I can only accept that
I do sense some quality link freshness has played a part as well - perhaps in the overall link graph/and build rate. Some folks resting on their older success' have slipped several slots.
appears likely to be correct, because that seems to be the only thing remaining - apart from conspiracy theories about googles motives of course...
I note also that the three 'brands' that have contacted us asking if they can write articles for us (we ignored them as we always do) in recent months (promising high quality articles and just one natural link...) do not appear to have been demoted.