For the moment, I think the entire Penguin fiasco has eclipsed the throttling issue. It's nearly impossible now to analyze the background throttling when you've been totally "throttled" by Penguin.
It's no longer Zombie traffic or throttling because now there is a measurable decrease in long tail. That clearly explains the current loss of traffic and sales. Prior to Penguin, serps looked good, there was no loss in traffic, yet there were very unnatural flat sales periods that had never been observed in prior years.
I have made one observation that points to a possible motivation. My Adwords cost is now equal to or greater than my Adsense revenue. This occurred with no changes on my part. In the past, for a sample week, I might take in $200 in Adsense and payout less than $100 in Adwords. Pretty nice balance I thought...now it's 50/50 and totally tweaked by Google's updates alone. The recent drop in long tail was what really balanced it out. I suspect that when Google felt they were losing the battle, they'd just shut off a portion of my long tail temporarily. Now they just eviscerated my long tail permanently.