1.4 billion using Facebook
700 million using WhatsApp
600 million using Messenger
300 million using Instagram
Messenger will be the driving innovator this year. At the 2015 F8 conference, FB introduced Messenger Platform. This gives developers a way to create apps that integrate directly into the app. You can reply to a message with a Meme Generator app, your friend can install the app and quickly reply back the same way. Yes, this is a crude example of how the app is powerful… But, even cooler, some eCommerce stores allow you to use messenger to be updated with your purchase. You can track your shipping and interact with customer service without having to login and authenticate, you just chat with the business through FB Messenger.
If you are a developer, check out http://messenger.com/platform