They positioned themselves very well in certain critical areas and I doubt that they will be easily replaced by competitors. For example in the ebook reader spa

They positioned themselves very well in certain critical areas and I doubt that they will be easily replaced by competitors. For example in the ebook reader space most competitors already went our of business and Amazon is now close to being a monopoly in this space. At this point they should be set up pretty well to increase their margins. I don't know how much percent of each ebook sale they take but similar to Apple's App Store I'm sure this is a nice cash cow.