The percentage of Google’s downstream traffic going to Wikipedia increased by 166% year over year (week ending 2/10/07 vs. week ending 2/11/06). Last week Wikipedia was the #3 website in Google’s downstream, after Google Image Search and MySpace.
Regardless of posturing, no business likes to send that much traffic to a third party site without some kind of value coming back. Will Wikipedia start running AdWords? Watch this space. I could imagine some kind of approach that drives revenue to the Wikimedia foundation….