Over 1 Billion users. According to wiki: According to the Financial Times, WhatsApp "has done to SMS on mobile phones what Skype did to international calling o

Over 1 Billion users. According to wiki: According to the Financial Times, WhatsApp "has done to SMS on mobile phones what Skype did to international calling on landlines."[167] Seems pretty world changing in terms of providing a core communication service to 1/7 of the human population