But Amazon doesn't do this to their vendors.
Take Books and Ebooks for a good example.
Regarding the major book selling firms, Amazon are the good guys because a relatively few book firms control the market. Amazon is helping to improve the customer experience by lowering the price of books.
they're replacing an oligopoly that is exploiting their customers with a monopoly though.
amazon hasn't really started exploiting its monopoly status yet (to my knowledge) toward the consumers, but a lot of authors have already started to complain about it.