"only seems worse because amazon is so big, and so monopolistic"
as:
"only seems worse because amazon is so big, and so dominant"
I don't think monopolistic is a fair adjective because it has an implied legal connotation. Is Amazon a monopoly or just the largest e-commerce retailer today?
Monopoly isn't the best term either, there's definitely other companies that are vertically integrated and are single-sources. What they don't do (or try to avoid?) is leveraging their position to unfairly complete with other companies.
Amazon launching new product lines and boosting them to the top of the search results is almost textbook leveraging. Having information showing they used their internal data to find which products to market is basically icing on the cake.
Google has already been dinged for this with their Google Apps boosterism on their search results. I can't imagine this goes any differently from that.
> According do US law, having 50% of the market can be enough.
Having much less than 50% of a descriptive market can be enough, if, e.g., you have pricing power, which demonstrates that irrespective of what other players may be described as being in the same market, they are not actually competing with you.
> Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power — that is, the long term ability to raise price or exclude competitors. That is how that term is used here: a "monopolist" is a firm with significant and durable market power.
only seems worse because amazon is so big, and so monopolistic, that a lot of people hold them to different standards.
It's the same idea that people expect a rich person to pay more taxes, or contribute more philothropically.