I came across Blogexplosion via Google Adsense itself. They were running an AdWords campaign and their ads were showing on my blog very often. Since I could not click on my own ads I had to type the URL (hopefully I had the type of ads that shows the URL) and that’s how I landed on Blogexplosion.
So Google is advertising a service that he does not want publishers displaying Adsense ads to use.
The time when the only way to advertise your blog is through Adwords might be coming soon.
Read about it on the official Adsense blog:Inside AdSense: A note on traffic exchange programs