mhansen - 11:14 pm on Jun 17, 2013 (gmt 0)
I probably heard this somewhere else in the past... but my feeling right now is that after a major update like this, the entire serp eco-system needs to regenerate over several weeks. Spam will rise to the top until it's re-evaluated by the latest algo recipe, and forced back down in the results due to poor [insert whatever metric here].
We were effected on June 9th with roughly 40% drop in Google referrals. We have lost no rankings in our highest volume referral phrases, however the longtail and obscure phrases are simply no longer delivering traffic, as if people stopped searching for them.