Not only is WhatsApp huge, it’s been growing like crazy. Right now, it has about 450 million users. And if you look at its growth curve compared to other popular services like Gmail, you can see why Facebook is willing to pay $US19 billion for the company.
In fact, WhatsApp is growing faster than Facebook did when Facebook was the same age. Impressive.
Here’s a chart from Facebook comparing WhatsApp’s growth to a few other services: