Sorry for the delayed response. You’re right — RTB will certainly slow down the adserving process. That being said, it’s *far* more efficient for two adservers to communicate together than an end-user to two different serving systems. Will write more on this topic.

-Mike

In your second diagram you show the interaction between the publisher adserver and multiple networks. Does this potentially multiple source back and forth not slow down the adserving in the same way a series of dumb redirects would? Especially when you consider that presumably if Network 1 came back with the best price out of 3 or four networks, once the publisher ad server knew that it would need to go back to it and request the actual ad again. It would be interesting to see some realistic HTTP traces for this stuff.

Also, for cookie based ad systems, per request visibility of the user to a behavioural network in this model would be harder to attain, no? The network in this case would need to “touch” the user in order to read the cookie.

Darren