Eric Schmidt gave an interesting answer to Senator Herb Kohl during antitrust hearings.

Senator Kohl: "But you do recognize that in the words that are used in antitrust kind of oversight, your market share constitutes monopoly, dominant--special power, dominant firm, monopoly firm? Do you recognize you're in that area?"

Mr. Schmidt: "I would agree, Senator, that we're in that area. Again, with apologies because I'm not a lawyer, my understanding of monopoly findings is it's actually a judicial process..."

https://www.gpo.gov/fdsys/pkg/CHRG-112shrg71471/html/CHRG-11...

Google doesn't have the "durable market power" described here: https://www.ftc.gov/tips-advice/competition-guidance/guide-a...

They can't raise prices and exclude competitors long term.

This internal FTC report that was leaked: http://graphics.wsj.com/google-ftc-report/

Has this conclusion: "Google has unlawfully maintained its monopoly over general search and search advertising"

The report ended up being buried, but it at least shows that credible people with lots of experience in the area believe strongly they are a monopoly.

That's a really great source. Though they do note that Google's market power isn't all that durable (because they don't charge, and competitors exist), they obviously conclude that they have unlawfully obtained monopolistic status.

You don't think Chrome's new ad blocker is an example of excluding their competitors in advertising?

> They can't raise prices and exclude competitors long term.

Of course they can–remember: they get paid by advertisers, but it's the users that make the decision to use them.

For many businesses, search is the only online ad channel that actually works, and it's not straightforward to see how any competitor could catch up to their technological advantage in search.

Technological advantage is a legal means to become a monopoly, according to the SEC link above.