I'd argue there's a very undefined grey line where companies cross over from just being a small scrappy startup doing something with tech to being a significant influencer of the public with a significant degree of control and impact. At that point it's in the interest of the general public to no longer treat them entirely as a private walled-garden enterprise but as something bigger.

We saw with the Microsoft antitrust case, the government stepping in where a business had grown to the point where it had a dangerous level of control and influence financially; I'm not sure if there's a social equivalent?