Here are three articles that give a good overview over that one service that is among the top5 downloaded apps (regardless of pre-installed apps like Google on Android) that dies not belong to Facebook: WeChat. Messengers are big, China is big, WeChat is huge. It now celebrates 5 years and - be strong now - made more transactions over Chinese New Year than PayPal made in the whole year of 2015.
Here's a good overview of the 5 year history of WeChat:
April 2015: great article about WeChat's influence on publishing:
WeChat NYE transactions in numbers: