Are you more or less forced to buy a Toyota simply because all your friends drive a Toyota? Is the majority of roads exclusive to Toyotas? If you question a business decision of Toyota, or a design of their car, can you then sell said car and purchase one from another brand with minimal impact on your daily life (Other than the fact that you have to sell and buy a car)?

Clearly it's not just about revenue numbers here.

I think nationalising Walmart is a perfectly reasonable idea. Considering issues like the level of access to quality food in poor neighbourhoods in the US and the fact that US government subsidises much of Walmart's labour cost already, it would be a much better deal for the American people on average.

Not really relevant, it's not the revenue that is a problem. It's their massive network effects that are, as the author puts it, platform monopolies.

Walmart, Toyota, Apple, do not have entrenching networks that lead to a monopoly. You can just as easily go to Target, buy a Honda, or get an Android phone