I'm going out on a very short limb here and say that everything that we have been suffering from is a major meltdown at google.
I believe that they are NOT deindexing...they just lost the data. Something happened when they instituted Big Daddy and introduced the new spidering system.
Nothing else makes sense. It is nothing we have done and there is not a penalty for anyone. It's all a huge glitch.
Google is melting down. And I can bet you they are seriously scrambling. I would love to be a fly on the wall in their engineering section.