Worth a read
People are starting to talk about the future of the online ad market. Worth a read:
http://www.attentionmax.com/blog/2009/03/the_endgame_of_media_buying_and_selling.php
http://www.mediapost.com/publications/?fa=Articles.showArticle&art_aid=103012
My bet is that it all will be exchanges and professional media buying platforms that incorporate targeting, data, interface and client services. It will be a lot like search and the SEM companies and platform developers. Should be fun.