My hope is that as these ad networks arise, they will keep (influential) people in the middle of the equation to curb pollution and keep the stream relevant. And that they are valued with the right metrics, which involves more than just subs, but links.
JohnBattelle's "Sell-side advertising" takes it further : http://battellemedia.com/archives/000844.php
Hmmm. isn't this the same as ViralMarketing?