I think one of the scariest effects will be the new entrenched power of the existing major sites.

Building a new Facebook, Google, Amazon, or Twitter after this will be more than a technical and social challenge. There will be literal gatekeepers charging a fee to compete in the same decent pipes.

Last time we saw the big sites speak up. This time it's only the users. It looks as if the big site operators are just preparing to pay to cement their position, damning the small businesses and independent creators.

This clearly benefits nobody except a small select few.

This might be my misunderstanding, but isn't that pretty much the definition of collusion?

I would say yes and agree with you but not if you have the money and lobbying influence to say its not.

That collusion would be no different than what is occurring today among the ISP. They have non written agreements to not compete with each other in certain areas , hence the lack of competition. This is how they can stay in business despite being rated the most hated companies in the US year after year by their own customers. Only way that can happen is if you are the only game in town (monolopy)

This is only branching out their arrangement to now include the existing Online Oligarch as well.

What separates collusion from a business agreement?

I would say transparency and a formal written statement between business, versus an agreement that is so unethical or illegal that nobody wants to put their name on it or officially declare it to the public.

A business agreement to mutually not enter one another's competitive domains is a conspiracy against the consumer. Similar examples include price fixing, anti-employee "poaching" agreements.

Permissable business agreements include joint ventures, plans to supply one another when creating or entering a new marketplace, etc.

Nothing.

Collusion is functionally an illegal (and informal) business agreement.

They’ll need all the power they can get. Decentralization is coming for them. If they’re not all terrified they should be.

I would love to believe this, but I'm not so optimistic.

I'm assuming you are referring to mesh type networks, in which case the hurdle is not technological but rather legal and political.

Once a mesh network becomes a valid competitor , they will create and enforce laws to hold people responsible for traffic going through their devices (ie kiddie P0rn and other illegal activities) .

They will also create and enforce anti encryption laws to prevent that as a loophole.

The challenge for mesh or decentralized networks will not be technical, it will legal and political which doesn't end well for the consumer.

Politics will be too slow to handle the rate of technological change. Already is to some degree. And Orwellian precincts will be at a competitive disadvantage.