Google released their SEC Filings for 2004, in it, many are discussing the topic of AdSense. Two forum threads are out and about; one at WebmasterWorld and the other at Search Engine Watch Forums.
The WebmasterWorld thread estimates that 77% of the ad spend driven by AdSense are going to the publisher. The Search Engine Watch thread estimates 60% of the ad spend is going to the publisher. Jenstar, in the SEW thread, has not yet reviewed the numbers in detail, but she was banking on the 60% figure for a long time now.
