Google Adsense says no to Traffic Exchange

I covered a story about StumbleUpon and Google Adsense here over two months ago. Last week, The official Google AdSense blog has posted another advisory about the use of Traffic Exchange programs:

As many of you already know, our program policies strictly prohibit any means of artificially generating ad impressions or clicks, including third-party services such as paid-to-click, paid-to-surf, auto-surf, and click-exchange programs. These programs offer incentives for users to view web pages or click on ads, resulting in activity that is harmful to our advertisers.

We occasionally receive questions from publishers interested in using traffic exchanges to bring traffic to their site. While these services may help advertise your site, we don’t recommend using them, as they may also result in similar invalid activity. We realize that you may have questions about a specific traffic service and whether it could potentially create invalid impressions or clicks. However, please understand that we’re unable to comment on any particular third-party service.

Although the Google AdSense Team does no directly comment on a specific 3rd-party programs, I’m assuming services like Blog Explosion, StumbleUpon, BlogMad and similar ones are flagged.