WhatsApp, Erlang, and the Power of Facebook→

Wired:

WhatsApp is owned by Facebook, after Zuckerberg and company paid $19 billion for the startup a little more than a year ago. That means Facebook now runs three of the most popular apps on the internet. Its primary social networking service is used by more than 1.5 billion people worldwide, and Facebook Messenger, an instant messaging service spun off from Facebook proper, spans 700 million. But the 900 million-user milestone announced by Koun is very much a WhatsApp achievement, not a product of the formidable Facebook machine.

In case you forgot how big Facebook is.