I'm an SEO and during our monthly reporting it became very clear that we were effected by Penguin. I did a search on two of our larger clients for 4/23 through 4/27 and it was like a spiral into h@#$&. We don't believe it was from on-page SEO and we are HUGE white hat proponents, but it would appear that our meta tags may be the culprit.
We are being proactive with our clients and telling them about the update and that they are going to notice alot of downward rankings. In the meantime, a lot of sleepless nights rewriting code and content. Ahh, the joy of being an SEO.
Does anyone know if we need to be proactive in resubmitting the sites in Webmaster Tools, or on a waiting game to see if the changes have been picked up in a positive way?