Sorry but you don't seem to understand how antitrust law works. Today, in the US and many other parts of the world, Google has a monopoly in the search market. Google is using their monopoly in that market to influence a second market (any one of a number of content verticals). It doesn't matter whether the service is free, or not free. Influence and unfair competition - this is the definition of antitrust. (How can any SEO or SEM expert ever compete against Google itself for search rankings or ad placements? They can't.) Microsoft tried to use its monopoly in OS to influence browser choice, and was rightly persecuted for it; this case is not much different.
In the US at least, you must prove that the consumer was harmed in order to have a successful antitrust complaint, and that's going to be pretty hard with google. With microsoft, it was a pretty clear pattern, ie rebates to OEMs to thwart competition. And more recently, disallowing users to change their default browser. Instead, with google, you can bid/get ranked high and you're still able to compete. You can install chrome and change the default search engine easily, etc etc. Google has been pretty careful about avoiding mistakes Microsoft made. And at the end of the day, if you don't like google, you type in "bing.com" and lo and behold, you're using another search engine. You could not (at the time at least)just install a competing OS within seconds.
Except that is not how antitrust works in the US. Competitors may be harmed if it is for the benefit of consumers. And it may not always be evident that the consumer benefits right away.
