petehall - 7:11 pm on Jun 18, 2013 (gmt 0)
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.
Did search suggest queries change at all? This could explain a fall in traffic despite rankings being similar.