> True, but the principle is a common one.
Its actually not as common as you might think; the principle in the US legal system that courts do not address hypothetical situations and issue advisory rulings distinguishes courts in the US system from courts in many non-US systems and many non-court adjudicative bodies (in the US and other systems.)
> And it is adversarial in that the Commission is prosecuting and Google is defending
Its more inquisitorial than adversarial, since there is not a separate prosecuting entity from the adjudicating entity, but the key point was that it wasn't between Google and its competitors, so its competition doesn't need to show anything, contrary to the suggestion made that the competition needs to show harm.
> To the extent that courts do not try hypothetical controversies, they also depend on actual proof and not unproven harm.
Only if the legal standard relevant to the controversy requires concrete harms. A prosecutor doesn't, for instance, have to show any harm when prosecuting attempted murder.
> How do you suppose a company would be found guilty of about-to-violate-antitrust-laws?
Antitrust laws very frequently prohibit conduct undertaken with the intent of monopolizing an industry, though the degree of actual harm is often relevant to the zeal with which antitrust authorities prosecute offenses, and the remedies imposed. Actual harm is often relevant in antitrust analysis, but may not be essential for a violation to occur -- just as the case for many other kinds of violations of law.