I think Farhad Manjoo gets it right about Amazon: while the company's sheer size, not to mention its often shady business practices, call out for public intervention, "Amazon is pushing a level of speed, convenience, and selection in shopping that millions of customers are integrating into their daily lives."
Breaking it up would be wrong, since the essence of what Amazon offers is its potential universality. For me, shopping on Amazon is almost like what I imagine shopping to be like in a socialist society, minus the lack of accountability and the astronomic riches of Jeff Bezos. Let's fix it. Make Amazon a public utility with proper protections for workers, consumers, and enterprises that use it as a marketing platform. Why not?