I've heard from a lot of webmasters now. It seems to have affected a great deal of sites that had, on Nov 15th, been authorities - and most of whom benefited from all the panda/penguin updates.
There's a hopeful consensus that it's a **misidentification** of some sort, muddied by the fact that many had not bothered with micro SEO for a long time (myself included)
I think we got too optimistic in the GoogleGuy days of "focus on content"!
Google didn't comment beyond the general guidelines. I'm trying another channel, I'll let you know how it goes.
I also learnt: Complaining about your traffic going down to 120k visits a day attracts a lot of trolling. We got treated like a bunch of whiny douches, they don't realise it took 10+ years of solid work.