WhatsApp is getting bigger and bigger as the years go by, but who would have guessed that such a simple messenger app could have over 250 million monthly active users? That's what the Wall Street Journal is reporting, and this is the first time WhatsApp has revealed hard numbers for its smartphone application.

What's really impressive about these numbers is that WhatsApp launched its app four years ago, and it only took that long for it to catch up to the likes of Skype, which boast 250 million users back in May 2012. However, in October of 2012, Microsoft claimed Skype has over 280 million users and it is not certain how much the service has grown in 2013. Furthermore, WhatsApp is even larger than Twitter at this point, as the popular microblogging site claimed back in December 2012 that it has over 200 million monthly users.

The fast growth of WhatsApp is a possible concern for many telecom operators, as users are making the switch to Internet-driven messaging apps instead of messaging the conventional way. Moreover, it is less expensive to send a message via WhatsApp than sending a text message, so no doubt telecom operators will soon experience a loss in revenue unless they join the revolution and make it easier for consumers to move away completely from SMS.

Many users have this belief that WhatsApp is free, but from what we come to understand, iPhone users must pay a one time payment of $0.99. Android and Windows Phone users get a full year free then after that must pay the $0.99 asking price. We're not fully certain how WhatsApp conducts business on other platforms, but it should be similar to the Android and Windows Phone approach.

Though WhatsApp is quite popular right now, the company need to be vigilant as BlackBerry announced that BBM is coming to Android and iOS in 2013. BBM is the original mobile messenger that began this trend, and it would come as no surprise if users make the switch.