WhatsApp hits 700 million active users

And, according to the company's CEO Jan Koum, that equates to 30 billion messages sent every single day.

When Facebook bought WhatsApp in February for an astonishing $19 billion, many believed that the deal would kill the social messaging app's appeal, especially among younger users. However, it appears that nothing could be further from the truth.

Back in February 2014 when the deal was announced, WhatsApp had 450 million monthly active users, meaning that over the past 11 months 250 million new users have signed up.

Much of the appeal of WhatsApp is that it is a very simple way of messaging anyone with an Android or Apple smartphone without incurring text-messaging charges and, apart from an annual subscription of $1 after the first year's use, the service is free. And the fact that Facebook hasn't interfered with that offering in any way or tried to rebrand WhatsApp or make it part of Facebook's own messaging service could well be why it continues to attract new users.

WhatsApp is expected to add free voice calling to the app in 2015 and to launch a desktop version so that people will be able to message and chat with friends while they're using their computers.