The home page of Google pulled up on a computer.
The home page of Google pulled up on a computer. - 
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Kai Ryssdal: The Wall Street Journal reported today the government's about to serve Google with subpoenas and launch a formal probe into it's anti-competitive practices. In English, that's anti-trust.

Marketplace's Mitchell Hartman reports.

Mitchell Hartman: Here's how big Google is: It handles more than half of U.S. search traffic and collects at least 75 percent of the ad revenue that search generates.

Joanna O'Connell is an analyst at Forrester Research.

Joanna O'Connell: They are almost a required player for marketers who are running search campaigns. You can't really do it without Google.

But having a monopoly isn't against the law. You have to use it to unfair advantage.

Scott Cleland is a research consultant who's testified against Google in Congress and his clients include Google competitors.

Scott Cleland: And what the FTC is looking into is, have they unfairly leveraged that monopoly to punish potential competitors, putting their products and their services number one in the ranking. And why that's significant is 34 percent of people click on the top result.

So concretely, a website like Yelp that's designed to search for restaurants may come up below a restaurant search result from Google Places. Same for YouTube, which Google owns, if I want to find a video.

Rupert Goodwins, editor of ZDNet UK, expects Google will defend itself as it has in a similar anti-trust case in Europe: saying it can't rig the results.

Rupert Goodwins: It's all done by computer. There isn't any way that they could put this sort of bias in. Which would mean Google revealing the details of how it does its searches.

And so far, Google's kept its secret search algorithm in a black box. But to defend itself, it may have to give a peak to the FTC.

I'm Mitchell Hartman for Marketplace.

Follow Mitchell Hartman at @entrepreneurguy