serpsup - 3:09 am on Jul 10, 2012 (gmt 0)
I've been noticing this trend as well for the past couple weeks. It may be correlated with summer, hot days in the US, or similar. Or it could be Google. I am an ecommerce affiliate and some days there will be a trickle of sales until after 6pm Eastern when the conversion rate goes way up. I haven't dug too deep to see if Google keywords / demographics are different during this time since I've just gotten used to fluctuations in keywords since I was bitten by Panda 1.0.