diberry - 7:40 pm on Jun 7, 2013 (gmt 0)
I've been looking into this, and apparently it hit more webmasters outside this forum and there was some discussion. The majority seems to believe it was Penguin 2.0 being tested on a subset of sites before being released into the wild. At least 4 sites hit by it were analyzed, and it looks like they all had both Penguin and Panda hits, so another theory is that it's a combo of Penguin and Panda, OR that Penguin 2.0 IS a combo of the two... sort of.
Just passing that along. Now that it's been nearly a month, I can say I've had an increase since then of over 300%. It's still way below what Google used to send me before Penguin, specifically because there are still a few of my pages that are way down from where they used to be. But those pages are up from where they had been.
Google's silence on this update does make me wonder if it was a Penguin test. I wish we could be sure, because there are so few stories of Penguin recovery (even partial) and I don't know if mine is that or not.