> I suspect it doesn't have anything like a majority share in the worldwide messaging space.
Whatsapp has 450 million users. The issue is that most Americans (and Australians, in your case) have never heard of it, so they assume that it's not very popular.
I have heard of it and have used it - I'm not surprised at the 450 million users figure, but the global messaging market is measured in in billions. Even people in third world countries use SMS - they do not have the ~90% marketshare which YouTube had when it was purchased.
In Australia it just, for some reason, never caught on - many people I know have accounts (as many as say, Instagram, for comparison) - it just seems to be something people try but don't stick with. Which in a sense, is a pity, as it's demonstrably better than SMS.
But in Australia Facebook Messenger already has the equivalent marketshare. Perhaps between Facebook Messenger and WhatsApp, Facebook would end with a majority marketshare [of IP-based messaging] as one app is popular where the other isn't. I honestly wouldn't know.
Whatsapp has 450 million users. The issue is that most Americans (and Australians, in your case) have never heard of it, so they assume that it's not very popular.
http://www.wired.com/wiredenterprise/2014/02/whatsapp-rules-...