flanok - 4:14 pm on Dec 3, 2013 (gmt 0)
I was also hit nov26th/27th on 2 sites.
With me, complete sub directories were removed from the index, yet others stayed with their rankings.
It all smelt of old Panda days.
All pages are, 100% unique etc, so do not get the extreme removal rather than just losing rankings.
So I would ask, have you lost pages, directories?
I am guessing a very small tweak has been made that affects a small amount of us to the extreme, leaving others untouched.
I had changed some internal anchor text on one site, after watching Matt Cutts explaining that anchor text in moderation within a site is OK.
But the second, I have not touched for months, if anyhing way more under-optimised than the competition with a better link profile.
The only common action was a bit of social media shares, on google plus, facebook and twitter the day before I was hit, sharing new content added.
Otherwise, I an completly unsure.
Check to see if any subdirectories have gone, it will be interesting to see in there are any similarities.