Shaddows - 2:39 pm on Aug 29, 2012 (gmt 0)
Perhaps Google now (after 8 weeks) has enough data to profile you. You could now be subject to personal search and query-intent matching.
If you're really lucky, you've only lost non-converting traffic. More likely, Google have been trading traffic for data, they have enough and now you are ranking on your on merits.