Ummm, I thought G was heading in the direction of site targeting by advertisers?
So, consistent with the idea that "choice of partners makes for more successful partnerships" it seems natural that Google would give publishers more granular control also.
My guess is that, in the end, the middleman that offers both advertisers and publishers the most granular control will win the most market share. That which gives G an edge in the selling of AdWords is not the same as that which affords G an advantage in selling "off campus" advertising.
In the absence of maximizing 3-party satisfaction(advertiser/aggregator/publisher) I can even foresee the evolution of an open source, quasi public ad marketplace arising - reminiscent of CraigsList. I wouldn't be at all surprised to see such a service in the very near future, where advertisers and publishers open engage in bidding for ad space and inventory.
Of course, G could keep its ad vehicle ahead of the curve by being more flexible, open and aggressive in in efforts to "open up control" - taking more away from "the middlewoman" - and affording more control to the real parties in interest: the advertiser and the publisher.
IMHO G's intermediation needs to be "driven to minimum settings" if G intends to survive and profit in open market advertising aggregation and delivery. That's, in part, where I think G is missing the boat in its 3d party advertising approach: More transparency, more choice, less control facilitated by greater choice, etc.