[loumf]

It's explained on the site. If every ad is clicked by everyone, tracking data is useless.

[jackmaney]

No, it isn't. Ad networks would have a clearer picture of sites that people visit (albeit a muddier picture of ad preferences).

[rvschuilenburg]

Clearer picture? I think just loading the ad is enough info for finding out what sites are visited. This just makes clicks less valuable.