1) Android, which was originally based on Linux, has become fragmented as many companies use different versions of Android. This fragmentation poses problems for developers.
2) Amazon modified Android for its Kindle Fire in ways that prevent it from supporting regular Android apps and allow Amazon to control users' web browsing and advertising experiences.
3) By making Android so open that it loses its brand identity and competitive advantages, Google has allowed others like Amazon to modify Android in ways that undermine Google's business model of using Android to generate advertising revenue.