Not from here, but rather from Kara Swishers post on Apple barring AdMob.
David K makes this excellent point:
Really? I never realized how I was held hostage. I could swear that I am completely free to buy any smart phone I want if I don't like the iPhone. I wasn't aware that I Apple would come send its iPolice after me if I walked into a Verizon store tommorow and picked up a Droid...
Since basically the argument in the preceding comments was along the lines that iAd was yet another instance of the closed ecosystem.
By the same token, devs aren’t held hostage as regards to their choice of Ad provider. This is made clear by the language in the new ToS. They just can’t use AdMob.
Quite frankly, Jobs has every right to bar Admob. To do anything else would be like Microsoft selling Lotus Notes in their stores. Not gonna happen.