WhatsApp – 500 million active users
Today, the authors of the WhatsApp messenger announced that they have overcome the mark of half a billion active users of the service.
Recall that at the end of December WhatsApp had "only" 400 million users. This means that in 4 months the messenger has gained 100 million users.
According to the development team, the main push occurred due to the growing popularity of the application in Brazil, India, Mexico and Russia.
I remember someone on the Network predicted WhatsApp's imminent death after Zuckerberg acquired the messenger in February. Some users even switched to Telegram. Judging by the increase of 100 million WhatsApp, a lot of users switched to Durov's brainchild.
Source: http://blog.whatsapp.com