Of course, this isn't really new (the Colorado experiment they reference was done in 2005), but this is a new analysis of the results. Essentially, the article discusses the reasons people tend to become radicalized and more homogeneous in their positions when participating in groups like DU.
The effect does make me vaguely uncomfortable, but I tell myself that rather than falling into "groupthink" it may be clarification and focus that drive the polarization effect. The entire article provides background on the experiment and what I thought was a pretty balanced discussion of the ramifications.
From The Chronicle Review
Volume 54, Issue 16, Page B9
Why do enclaves, on the Internet and elsewhere, produce political polarization? The first explanation emphasizes the role of information. Suppose that people who tend to oppose nuclear power are exposed to the views of those who agree with them. It stands to reason that such people will find a disproportionately large number of arguments against nuclear power — and a disproportionately small number of arguments in favor of nuclear power. If people are paying attention to one another, the exchange of information should move people further in opposition to nuclear power. This very process was specifically observed in the Colorado experiment, and in our increasingly enclaved world, it is happening every minute of every day.
The second explanation, involving social comparison, begins with the reasonable suggestion that people want to be perceived favorably by other group members. Once they hear what others believe, they often adjust their positions in the direction of the dominant position. Suppose, for example, that people in an Internet discussion group tend to be sharply opposed to the idea of civil unions for same-sex couples, and that they also want to seem to be sharply opposed to such unions. If they are speaking with people who are also sharply opposed to these things, they are likely to shift in the direction of even sharper opposition as a result of learning what others think.
http://chronicle.com/temp/reprint.php?id=w218t7yc6kv2lh...