Who else is it about? If any sort of investigation is to be brought into it, the main investigation would be on behalf of consumers right?
> "single-handedly makes up 4% of the US economy"
Correction: 4% of the US stock market, not the US economy.
Regardless, is your argument that any company that is at a certain threshold % of the US economy/stock market should not do acquisitions or expand their business?
Economists do get it wrong. If you think this will reduce consumer welfare (which is one of the standards used to judge mergers), tell me how.
I see no reason to block the merger on the grounds that Amazon is a trillion dollar company, rather than a 900 or 800 or whatever billion dollar company.
Amazon is not 4% of the US economy, btw.