bill - 2:06 am on Mar 1, 2012 (gmt 0)
An interesting local take on why Google hasn't succeeded in Korea.
Why Google Is Not Popular in Korea [clickz.asia]
It's not only the language barrier but most Korean websites are still built with flash links and full text images. It is not a good situation for Google to crawl information from websites in Korea and it leads to lack of quality results on Google's SERP in the country anyway.
Even some web hosting companies blocked access of Google-bot to avoid overload of traffic from Google. The worst thing is most clients didn't know that the web hosting company has blocked their sites.