But after actually running the server for experimental work and watching the company grow, things are really changing in the open source or other ad networks. ReadWriteWeb has a good article, on the status of the OpenX, the company behind the OpenAd server.
RWW, aske the company how it is going to challenge the growing Ad markets with many ad networks. The answers are;
1) OpenX is an independent, neutral provider
2) The second difference between OpenX and Ad Manager is that OpenX is open source and "infinitiely customizable".
3) The third difference is that OpenX is "very very feature rich" compared to other ad servers - and not just Google's.
But the RWW article has much more information. As for me, yes it seems that Open Source Adnetworks does seem to have clout.