BRUSSELS – The coast is clear for the merger of Google and DoubleClick. European regulators on Tuesday signed off on the search giant’s proposed $3.1 billion acquisition of the Web’s largest banner and video advertising network.The European Commission ruled “the transaction would be unlikely to have harmful effects on consumers, either in ad serving or in online advertising markets.” The U.S. Federal Trade Commission approved the acquisition in December.

Google, understandably, is happy about the decision. The addition of DoubleClick to its growing roster of purchased technology companies strengthens Google’s position against rival Microsoft, which also has been snapping up advertising-related properties lately. Both companies have faced scrutiny domestically and internationally because of the potential to abuse consumers’ private information in the race to corral hefty shares of the online advertising market. The key, industry watchers agree, is to gather huge databases about consumer online behavior, and DoubleClick’s database is one of the largest in the world.

Not everyone was elated by the news. Privacy advocates continue to argue that the concentration of such large amounts of consumer information — particularly of the sort gathered by advertising firms and search engines — in such a few hands bodes ill for the public. Oddly, Microsoft sided with the privacy advocates, even though the Redmond, WA-based software giant in May 2007 spent $6 billion to acquire aQuantive for similar reasons.

But Google and Microsoft have a bigger bone to pick: Microsoft’s proposed $44.6 billion takeover of Yahoo!, which Google says would give Microsoft far too much control over not only search-related advertising, but also over the instant-messaging and email markets. Yahoo isn’t wild about the acquisition either, and continues to stall Microsoft’s hostile bid.