Nowadays almost every mobile app has a function to easily share content on social networks such as Twitter, Facebook or Whatsapp. This is crucial for commercial distribution of mobile apps.
C3 should be able to provide a function to accomplish this. Posting short notifications alongside showing an icon of one's app would be nice.
An official Share plugin shipped in C3 r121. It currently only supports mobile, but it is based on a standard API, so should cover desktop platforms in future as browsers add support there.