Korean romanization was a major thorn in my side during the 1990s, when I worked as an editor of academic articles and books in English about Korean history, culture, and language. At that time, the McCune-Reischauer system prevailed in most academic fields, but the Yale system prevailed in linguistics. In 2000, the South Korean Ministry of Education issued Revised Romanization guidelines that eliminated the need for many diacritics that were often omitted on the Internet. The ROK system now seems dominant in popular usage, but romanization still remains chaotic, as this recent Language Log post well illustrates.
I don’t wish to open the whole can of worms here, but just to illustrate a bit of the chaos with examples of how a popular Korean food, 떡볶이 (ttekpokki in Yale transcription) ‘stir-fried rice cakes’, is romanized on signs and food packages in Korean restaurants and markets in Honolulu. The Korean spelling is consistent in every case, but the romanization varies a lot. Wikipedia romanizes the name of the dish as Tteokbokki; a long-time Korean restaurant (which initially prompted this post) spells it Derkbokee; another restaurant spells it Tteobokki; and some packages in a Korean supermarket spell it Tteok-bokki while others shorten it to Topokki.