As new Platform-A President Greg Coleman indicated last month when he shuffled the decks at the AOL ad unit, the company has finalized its shift away from Google-owned DoubleClick’s ad system to AdTech, the German ad serving company AOL acquired in May 2007. 

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AdTech head Dirk Freytag, who now takes on the title as Platform-A SVP, says the moving the ad-serving functions in-house will save millions of dollars. So why did it take so long to move away from DoubleClick’s system? Well, it could signal that AOL feels it finally wants to compete against DoubleClick, as Google (NSDQ: GOOG) has asked Time Warner to buy back its 5 percent stake in AOL (NYSE: TWX). In January, Google took a $726 million writedown on the $1 billion investment it made in AOL back in 2005. At the time, the alignment helped Google decisively win the search race against Microsoft (NSDQ: MSFT). But now, the relationship appears to have soured, especially since Google’s top ad exec Tim Armstrong is set to take the reins at AOL early next month. Release