Forbes published an interesting article about how Brian Kim, the cofounder of Kakao Talk has become one of South Korea's richest billionaires. The service, which was only launched in 2010, is now used by 93 percent of domestic smartphone users, or nearly 75 percent of the nation's population. As noted in the article, "While Kakao, in Pangyo–south of Seoul–has certainly aimed globally, its greatest success has come at home. It boasts 50 million users who are active monthly, of which three-quarters are Koreans who’ve ditched SMS text messages for the ease of KakaoTalk.
As illustrated in the accompanying graphic (click for a larger version),Some of Kakaotalk's "...biggest competition comes from his old company, which started its own mobile messenger, Line, a year after KakaoTalk began. Once derided by Kakao fans as a copycat, Line has come nowhere near dethroning Kakao in South Korea, but it has become the dominant messaging service in Japan and has made a wider global impact.