POSN is a decentralized online social network that is cenered around a peer-to-peer infrastructure and utilizes free cloud storage to store user data. Each user has full control over who can access their data through the use of encryption.
Getting Started: https://www.dropbox.com/developers-v1/core/sdks/android
API Reference: https://www.dropboxstatic.com/static/developers/dropbox-android-sdk-1.6.3-docs/overview-summary.html
Getting Started: https://developers.google.com/drive/android/get-started
API Reference: https://developers.google.com/android/reference/com/google/android/gms/drive/package-summary
Getting Started: https://msdn.microsoft.com/en-us/library/office/dn631814.aspx
API Reference: https://msdn.microsoft.com/en-us/library/hh846809.aspx