http://www.hpl.hp.com/research/scl/papers/howopinions/wine.pdf How web discourse evolves. To appear in the Proceedings of the Workshop on Internet and Network Economics-2008 opinion formation social networks polarization crowdsourcing WINE No aspect of the massive participation in content creation that the web enables is more evident than in the countless number of opinions, news and product reviews that are constantly posted on the Internet. Given their importance we have analyzed their temporal evo- lution in a number of scenarios. We have found that while ignorance of previous views leads to a uniform sampling of the range of opinions among a community, exposure of previous opinions to potential review- ers induces a trend following process which leads to the expression of increasingly extreme views. Moreover, when the expression of an opinion is costly and previous views are known, a selection bias softens the ex- treme views, as people exhibit a tendency to speak out differently from previous opinions. These findings are not only robust but also suggest simple procedures to extract given types of opinions from the population at large. Fang Wu and Bernardo A. Huberman 2008-09-11 12:00:00