

Zuckerberg reiterated that Messenger and WhatsApp will not be integrated. Still, he says “one our theories is that you need a large established network of people who will be able to receive the calls” for VOIP calling to become popular.
With 600 million Messenger users and 800 million WhatsApp users, he thinks they’re both finally hitting that critical mass. And just today, Facebook released its caller ID app Hello that lets you easily ignore normal phone calls and then Messenger VOIP the person right back for free, which could further boost usage of the feature.
Meanwhile, Messenger is still exploding as a text message alternative.
At this rate, messaging is beginning to look like a Facebook-dominated game outside of China. With Messenger popular in the US and WhatsApp winning in Europe and the developing world, it’s only China where Facebook can’t operate that another service, WeChat, is on top in a major market.
While Facebook might not try to monetize phone calls or text messaging directly, Messenger drives usage of Facebook’s social network where it earns money on ads. Zuckerberg said “We’re not going to charge for it, the way we’re not going to charge for text messaging. We’re focused on offering higher quality services for free than you can get by paying for them.”
It’s a unique strategy that gives Facebook a huge advantage on mobile where cramming ads and payment channels everywhere can feel obtrusive. Instead, Facebook can keep most of its apps and experiences clean and free since it makes so much money on ads in its main app — $3.32 billion in Q1 2015 alone.