BuddyPress.org

You could try our Buddypress Ads Plugin available at https://wordpress.org/extend/plugins/buddypress-ads/

This plugin will allow you to publish ads through your buddypress site(with wordpress mu) Supports multiple ad networks including adsense , adbrite and many more. Just replace the ad code in the file bp-custom.php with your own ad code.

More details at http://www.pingsense.com/2009/11/buddypress-ads-plugin/