I noticed on one of my clients sites that has Adbrite cod on there page and it is serving Adsense ads in that block. Has Google struck a deal with Adbrite to allow them to serve Adsense to third parties?
Upon taking a closer look. It looks like the publisher id is for the owner of the site. Leads me to believe Adbrite may have a provision to supply a Clients Adsense if they don't have any ads available for their site. Strange. The source code is Adbrite js and the ad displays Google.
i think htere is an option in adbrite as if ur using other ad services it generate a code in such a way that the ads that will earn u the most is showed like if adbrite ads at that time are cheaper then adsense it will show adsense and vice versa for the publisher to earn the maximum revenue per click
It is a old time provision given by adbrite, where in you can provide them with your adsense id while signing up for adbrite and if they are not able to match the adsense cpm or earnings or when there are no ads to show then google ads will show up
With adbrite you can include any other external ad networks ads while people bid/buy yours or while you don't have any advertisers.
AdBrite has a facility/mechanism by which it can display ads from other ad networks if AdBrite does not find any related ads from its own network. Hence, it can be the case that your friend has setup this mechanism to serve Google ads if AdBrite ads are not available.