Strange Google Adsense Ads

While the adsense publishers are discussing about Google Checkouts I Discovered another interesting thing.

• Few Minutes back when typed SEO in Google Search Box , I saw telephone ICON near the Ad title.
  

• When Clicked on that Icon , I found following.
  

Generally when Some one clicks on the ad , the user is diverted to advertiser's website , but in this case he/she provide his/her telephone number to google. Google will call the User. Can we call this Cost per Action ? Will google pay the money to the adsense publishers only when sales is made ?