Naver (www.stock.naver.com) is the largest online portal in South Korea. On top of dominating Korean language search and launching a wildly successful instant messaging service ‘LINE’, it also owns a financial services domain, with services including financial news, stock quotes, exchange rates, corporate press releases, reports and recommendations. Naver also runs the largest stock message boards in the country. In 2010, Park Jae Hong and his team of researchers conducted a very interesting field experiment. Respondents were investors participating in online discussion forums. They were first asked to fill in a short questionnaire and to state their outlook on the stock in question. For example, if they were participating in a discussion on Samsung, they will be asked to rate the stock either as a strong buy, buy, hold, sell or strong sell. The researchers then tied up with Naver to manipulated the forum by creating five ......