Google blocked South Korean users from uploading videos and posting comments on YouTube's Korean-language site in order to avoid government requirements for the real-name registration of users. Korean Internet users now have to submit their resident registration codes, the Korean equivalent of social security numbers, and names, before posting files or commenting on Web sites with more than 100,000 daily visitors, including YouTube. The new rules kicked in April 1, but Google had been refusing to enforce real-name verification for YouTube users, reluctant to bend its rules only for Korea," reports KoreaTimes.

More info: Google Korea blog | YouTube Korea blog