An economy dominated by Amazon isn't a market economy - it's a planned economy, run by Party Secretary Bezos to benefit Amazon's shareholders.
Now, there *is* a role for a business regulator, because some businesses really *don't* deserve to live (they sell harmful products, engage in deceptive practices, etc). The UK has a regulator that's in charge of this stuff: the Competition and Markets Authority, which is now going to be run by Jeff Bezos's hand-picked UK Amazon boss.
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