Andem - 2:27 am on Jun 7, 2013 (gmt 0)
Do you happen to have ads above the fold?
I only have ads on around 20% of pages, which make up around 12-13% of pageviews. They aren't really above the fold, but more half-above and half-below in most cases while content and recommendations for other pages on our site are much more prominent.
In any case, I can't say whether any algorithm updates are having any effect as opposed to normal growth patterns when it comes to search result referrals.