It's no secret that piracy — especially game piracy — is widespread in South Korean. While there is no data, Gamasutra's Nick Rumas points out that it's evident to anyone with "a pair of eyes". Rumas takes a look at how the R4 is used in Korea, writing:
In Korea, piracy of video games isn't limited to the hardcore crowd; it's everywhere, prevalent in every age group and economic class that exists. And beyond being a matter of money - of not wanting to spend money, that is - piracy for Koreans is, perhaps even foremost, a matter of convenience.
Interestingly, Rumas points out that many Korean R4 owners aren't even that tech savvy and simply purchase pre-loaded flash cards! Swing by Gamasutra and check out the article. There's some some good insights there and good questions asked about Nintendo's piracy fight in Korea.