Just found out that Google's AdSense Referrals program ends during the last week of August. I used to a few referral ads on this blog but right now the only one is the Firefox with Google toolbar ad banner at the bottom.
The email from Google recommends joining the DoubleClick Performics Affiliate Network, which is now part of their empire.
Do remember to remove the referral codes from your site before the last
week of August.
For more information check out the Google help centre.