Have you actually seen the proposal? It's not specifically about Facebook, they just happen to be a good example of market failure that she wants to prevent.
I read her blog post. I don't see anywhere in her post that gives one concrete example of a negative impact on consumers.
She gives the example of Amazon.com forcing diapers.com to sell diapers at a lower price as a reason for why we need to prevent acquisitions. But getting products for cheaper prices benefits consumers... The small business founders got rich and consumers got cheaper diapers. I'm not seeing any problem with that.
She claims Amazon is anti-competitive because they promote their own products on their own website. Websites aren't railroads. Consumers can choose any website by typing in the address in their web browser. Consumers can switch search engines and shopping websites. That was not the case with railroads or phone networks - because for reasons that should be very obvious you can't have a million different railroad lines and telephone wires. Unlike the web, they were physically mutually exclusive.
If a company provided superior service and prices to Amazon consumers can easily choose to use them.
You might find a problem with that arrangement when you need to buy something that Amazon doesn't or won't carry, and there's nobody else in town (because they can't survive on such products alone). Or as a manufacturer who makes a new and better product compared to something that they have, but who can't find a sales channel for it. Or as someone who is unhappy with some of Amazon's practices - say, how they treat their employees.
And competition doesn't just show up out of thin air - you need a healthy free market for companies to get to the point where they can challenge the market leader. If you allow the monopolist to dominate the market, they will never get there, and there won't be anything for consumers to easily choose from.
In general, concentration of power is dangerous. Few people dispute this with governments - it's not like we wait for them to become authoritarian, we write constitutions that have arrangements that deliberately cripple their ability to do so (separation of powers etc). Why should it be any different for large corporations, when we know from history that monopoly abuse is the most likely outcome?
She gives the example of Amazon.com forcing diapers.com to sell diapers at a lower price as a reason for why we need to prevent acquisitions. But getting products for cheaper prices benefits consumers... The small business founders got rich and consumers got cheaper diapers. I'm not seeing any problem with that.
She claims Amazon is anti-competitive because they promote their own products on their own website. Websites aren't railroads. Consumers can choose any website by typing in the address in their web browser. Consumers can switch search engines and shopping websites. That was not the case with railroads or phone networks - because for reasons that should be very obvious you can't have a million different railroad lines and telephone wires. Unlike the web, they were physically mutually exclusive.
If a company provided superior service and prices to Amazon consumers can easily choose to use them.