Moderator, AussieWebmaster at Search Engine Watch forums reports that Google will be changing the AdWords policy to only allow "Google is going to restrict the number of affiliates that can send traffic to the same place (tracking/affiliate code not counted)." What this means is that if you are an affiliate for amazon and you send traffic to amazon.com, then the only way for me to send affiliate traffic from AdWords to amazon.com would be to outbid you. Only one Adwords customer can own a page or URL (not including the tracking code) at a time. AussieWebmaster continues, "The criteria for who gets the ad will be based on rank (CTR and CPC)... though back-ups will be in place for when the spend is gone for one so another can come in etc."
Very important information for you affiliates that use AdWords. These changes are expected to take place after the holiday season.