In the discussions of freedom of expression and media responsibility, there existsa familiar metaphor of "marketplace of ideas".The concept is borrowed from free-market economics, in such a market, truths and lies compete with each other,and it is expected that the former will eventually overcome the latter. This market model can be naive and misleading, however, it also serves as a convincing argument in that it emphasizes the importance of freedom of expression, as well as the benefits of information flow in the free exchange of ideas. This paper tries to put "marketplace of ideas"in the Internet context, to see its applicability in the new information environment, as well as the impact of large-scale participation upon the concept.