They actually just did. They argued that Google is free, and there's nothing to prevent users from using a different search engine. The argument seems to be that a large market share does not constitute monopoly power. In order for monopoly power to exist, there have to be barriers preventing users from switching search providers.
> In order for monopoly power to exist, there have to be barriers preventing users from switching search providers.
That is incorrect. A "monopoly" is simply having a large enough control over the market that you dictate how others access that market. Monopolies are not illegal. Google does have a monopoly on search, Schmidt admitted that much today by saying they are "in the area" of having one.
Abusing your monopoly power is however illegal, and that's what Google is being investigated for.
However the principle that underwrites all of it is harm to the consumer. If you can't prove harm then it is hard to justify action. If consumers are choosing the monopoly provider willingly with zero compulsion by factors other than that it serves them well then you have a good argument that the monopoly is not harming the consumer.
The best argument would be that the purchasers of advertising are harmed because Google's ad prices are bolstered by their monopoly on search. However even there, Google uses a quite transparent and open bidding system for ads. They have no direct control over what people pay, they don't set their own prices - Google only shows ads at the prices people voluntarily bid. This doesn't put them in the clear but it makes it pretty hard to prove they are gouging or any of the other obvious signs of a monopoly abusing their power.
