Yesterday, Apple finally updated its developer agreement to allow independent advertising companies. But at the same time it blocked ad firms owned by companies that make mobile devices and mobile operating systems. As All Things Digital points out, that shortlist currently includes Apple’s biggest competitor in mobile ads — Google-owned AdMob.

Today, AdMob CEO Omar Hamoui responded to the snub, and made it clear why he thinks it’s a terrible idea. “In the history of technology and innovation, it’s clear that competition delivers the best outcome,” he writes, “Artificial barriers to competition hurt users and developers and, in the long run, stall technological progress.”

Ever since Apple changed its iPhone Developer License Agreement in April — which banned third-party app analytics tools, and in the process appeared to lock out third-party mobile ad firms from displaying in-app ads — it’s been unclear how the company would deal with mobile advertising competitors. Now we know it’s far from a worst-case scenario — instead of locking all competitors out, smaller ad companies will be able to collect user data to sell ads (with Apple’s approval). But the wording is definitely vague, and the new rules could easily be used to lock out an independent ad firm like Millenial Media if it’s purchased by the likes of Microsoft or Yahoo.

At Apple’s Worldwide Developer Conference this week, Steve Jobs presented a slide that predicted 48 percent of mobile ad purchases for the second half of this year will come through its iAds advertising platform. Given its lofty ambitions, there’s little reason for Apple to open up its mobile platforms to all advertising networks. It’s also well within Apple’s rights not to. But considering that Google’s purchase of AdMob was delayed by six months for FTC approval, acting so brazenly anti-competitive may not be the wisest choice for Apple.

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