Google recently updated their AdSense terms of service and one publisher asked AdSenseAdvisor if Google AdSense is or will be using "web beacons."
After about a week (March 18th), AdSenseAdvisor replied to a WebmasterWorld thread saying:
In the future we may begin to serve new ad tags that may use web beacons to help advertisers track their metrics.
Is this a huge deal? I am not one to talk about privacy and stuff like that (I am one of the most public people out there). But I do know that Facebook and other companies received a lot of flake over web beacons. Not sure if this would or will make much of a privacy difference in Google's case. Google already uses plenty of tracking mechanisms with Google AdSense.
But the addition of adding new ad tags via web beacons is a new implementation to AdSense that might be coming soon.
Forum discussion at WebmasterWorld.