[rexignis]

I've lived in Korea, my experience was you gave out phone numbers when meeting new people, KakaoTalk automatically scans new contacts and adds them to your KakaoTalk contacts and all subsequent texting and photo sharing was through KakaoTalk.

I only texted one person regularly while I lived there, my boss; my boss had a KakaoTalk account but didn't use it (with me at least).

I still use it, it's a very good messaging application with some pretty well implemented features (and excellent custom emojis!).

[sho_hn]

KakaoTalk is very well realized and really fun to use; the privacy side leaves me queasy, though. KakaoTalk conversations are known to be under government surveillance, and the KCSC is a troublesome institution in general (cf. http://opennetkorea.org/en/wp/administrative-censorship).

[dba7dba]

Ever heard of NSA?

[ericdykstra]

Currently living in Japan, and I haven't given my phone number out to anyone yet. It's all exchanging LINE info (mostly using the QR functionality, sometimes just the ID). Almost everyone has a Facebook, but I don't think the messaging component is widely used. Almost all messaging, and even most voice calls, go through LINE.