When you compare Amazon to say Walmart or Google, I think the real consideration is that the later two have narrow verticals of dominance and Amazon's dominance spans e-retail, compute, storage, etc and is expanding. Having one entity control 60% of 50 verticals is much more dangerous for the economy anti-competitively than one company that controls 80% of say two verticals. The reason is simple they can use their multi-vertical footprint to apply pressures on a small competitor that a large competitor who was limited to a single vertical could not.