>>> In Korea, all most people are using KakaoTalk (android app).
>>> If i am wrong, sorry, and let it go to off-topic.
>> It's not decentralized. IOW you're dependent on one central
>> server/company and everything goes through them, they get an insane
>> amount of data and power this way.
Of course, another major problem with it, AFAICT, is that there's no
Free Software client for it.