Google may be purchasing DoubleClick for $3.1 billion, but Microsoft is saying “not so fast.” They too were in on the bidding for DoubleClick and lost, which had to have stung pretty bad. Now Microsoft is protesting the proposed sale, and they also expect other companies like Yahoo and AT&T to join them.

The New York Times is reporting that Microsoft is claiming that the deal would “hurt competition in the fast-growing market for advertising on the Web and raise questions about how much personal information would be collected by Google.”

Microsoft is usually the target of these antitrust battles, and now they find themselves on the other side. AT&T is already saying that antritrust authorities really need to take a look at this deal, and Microsoft is saying that if this deal goes through, Google would be master of 85 percent of the market for ad distributing and they need to be stopped.

Google’s response to all of this is that they’ve taken a look at their claims and it’s not true. Along with Microsoft, Yahoo was also in on the bidding for DoubleClick, and they’re expected to step up and express their concerns over this deal as well.

So here we are with Microsoft, the king of anti-trust, hoping to stop Google in their tracks before they become a monopoly. Ironic, isn’t it? Although, maybe Microsoft does have a point here?