@ Planet -
Similar situation here. We got hit partially by one of the later Panda updates, but not enough to really hurt ecommerce sales too bad. Penguin 2.0 was not kind though. Wish I could say sales were up.
Thank you so much for sharing your information and story. We cerntainly don't do anything wrong or black hat, but Google honestly keeps changing the "rules" so you never know. There are things that Matt Cutts advised that were OK or even enouraged 7 years ago (focus on relevant anchor text backlinks in good content), that now are "against the rules" if you were too good at it and those same techniques can cause over-optimization penalties if you did "too much" of it. Been at this for 13 years and the site is even older so what was encouraged and white as white hat can be might now look like gray hat.