Facebook's $19 billion deal to buy WhatsApp is causing a buzz in the tech industry as well as on Wall Street.  

TechHive associate editor Caitlin McGarry says the international appeal of the mobile messenger app was clearly a factor.

"Mark Zuckerburg, Facebook CEO, has talked a lot about connecting the world to the Internet. And the fact that WhatsApp is an app that 450 million people use every month was really key for them," McGarry said. 

McGarry says many of WhatsApp's 450 million users take advantage of the free service as a replacement for text messages, which can be very expensive in other countries.  

McGarry also notes that Facebook had its own messenger app, but now owns its biggest rival with the purchase of WhatsApp.