http://forum.wordreference.com/threads/ex-for-example.1772384/ It's the abbreviation used in French (and possibly other languages). I don't think they teach the use of this abbreviation in English classes, manuals or courses, it's just that people not familiar with English will assume it works in English as well and use it instead of e.g. because they're not aware of e.g. Koreans are accustomed to use ex. or ex) for abbreviation. Most of school textbooks use ex.

The English way of writing eg comes from the latin "exemplum gratiae," roughly meaning for example. I am not sure why the Koreans write ex

You just got a glimpse of Konglish.

I'd like to add Park's opinion that Korean have no idea whatsoever that eg came from Latin, exempli gratia. They use 'ex' to stand for 'example' because it's easy to write on a black board when teaching students in school without realising it is wrong from the naive speakers point of view. When I was in middle school, I saw even my English teacher using it.