I don't see the problem. It's Amazon's money; they are entitled to spend it however they want.

I think a lot of people are mad at Amazon for various things; undercutting mom-and-pop businesses in niche markets, paying people to deliver packages almost for free, busting warehouse unions, counterfeit items, etc. The solution is to not fund Amazon. Move your servers elsewhere. Shop at Target. Ask your representatives to make stronger labor laws.

But all in all, I don't think it's intrinsically wrong to start selling an internal tool and then end up making a lot of money from it. If Amazon weren't dominating online retail, someone else would be. Nobody wants to go to a store. It's boring and there isn't a very good selection. That is not the fault of cloud computing.