Baidu dominates China, though its spill-over popularity into neighboring countries makes the researchers doubt whether data from those countries is accurate.

The data for Korea clearly isn't accurate. Baidu is almost unheard of in this country. Not many young people can even read Chinese. Naver, a local company, dominates 70% of the Korean search market and a significant portion of the social networking scene as well. Its anti-competitive behavior is currently a hot topic in Korea.

I suppose the anomaly is due to the fact that the authors used Alexa (mentioned in the bottom right of the second image). Hardly anyone in Korea has the Alexa toolbar installed. People here, like elsewhere, pollute their PCs with all sorts of other toolbars, but rarely Alexa. The language barrier probably plays a part. I wouldn't be surprised if those who do have Alexa (usually foreigners) tend to have ties to a certain neighboring country with a very large population.