Undeniable, Apple introduced the first App store in 2008. Nowadays, the app store is still developing rapidly. Amazon App Store, Apple App Store, Google App Store, Palm, RIM and Windows Phone marketplace. Android has become the top smartphone platform among all of them. There were 5 billion apps were downloaded in 2010. Wow.. the number is keep on increasing and estimated to reach 21 billion in 2013. See more details in Infographic below.