http://www.whizzbangsblog.com/content/view/297/86/

More interesting perspective from Michael per yesterday’s post… Some great charts too. He surmises that Google’s TAC (traffic acquisition costs paid to syndicators/affiliates) is increasing and its margins are falling as it engages in a war to deny traffic to competing keyword marketplaces. I have heard several publishers hypothesize that there is an unspoken "screen" or "discard rate" applied to traffic in the major keyword marketplaces. 

Even if this is just a figment of paranoid publishers imaginations Google’s black-box and record earnings just don’t add up against flat publisher revenues..  a bit more transparency on Google’s part would likely drive more publisher loyalty, longer commitments and trust.