Google is not the boss in South Korea.

Yes, Google's interface is very simple with one search box, and it is the leading website/search engine in the world. However, that's the not case in South Korea. Google is not the leader in that country. People in South Korea are considered some of the most internet-savvy in the world. According to WebSideStory (Web Analytic company) Google represented about 17% of unique visitors in March, 2006.

Who is the leader in Search Engine in S Korea then?
Its called Naver.com (Korean site), which links accounted for about 58% of search referrals. Daum communications was in second place with more than 48% and Yahoo Korea with 32% landing in third position.

Why is Google lagging behind?
Unlike Naver, and Yahoo, Google's search relies heavily on a software. Naver is driven by human expertise to deliver search results. Other feature of Naver is called "knowledge iN" that has help create a database filled with questions and answers. Users can ask questions and are answered by other users. It now totals over 4 million entries. Such feature has been attracting South Koreans internet users to Naver where they interact with other people. So basically its a "people-created" website.

Despite advertisements/publicity/spending by Google in S. Korea, it still is lagging behind sites like Naver.com.

Google.com can not be the boss in every country.