Kakao's business model history is actually rather fascinating, and they keep grabbing sizeable market shares in unlikely or previously inexpressive markets to great success.
> In 2012, KakaoTalk's $42 million revenue is broken down to 67.5% ($31.1M) gaming, 26.2% ($12.1M) advertising, and 6.3% ($2.8M) emoticon sales. [1]