An academic paper on the differences between left and right (with some sites as 'central') web sites - mainly blogs, but including forums such as DU. Here's the abstract:
In this paper, we revisit these findings by comparing the practices of discursive production and participation among top U.S. political blogs on the left, right, and center during Summer, 2008. Based on qualitative coding of the top 155 political blogs, our results reveal significant cross-ideological variations along several important dimensions. Notably, we find evidence of an association between ideological affiliation and the technologies, institutions, and practices of participation across political blogs. Sites on the left adopt more participatory technical platforms; are comprised of significantly fewer sole-authored sites; include user blogs; maintain more fluid boundaries between secondary and primary content; include longer narrative and discussion posts; and (among the top half of the blogs in our sample) more often use blogs as platforms for mobilization as well as discursive production.
http://cyber.law.harvard.edu/publications/2010/Tale_Two_Blogospheres_Discursive_Practices_Left_RightI think DU contributes a lot to "(s)ites on the left adopt more participatory technical platforms". DU is mentioned once explicitly in the report:
And when you think that FR is so technically naff, DU admin can feel proud of some of those large blue bars.
So, the basic conclusion is: the right has largely stuck to single authors holding forth with their own opinions in one format, and the readers just get to comment. The left has come up with many more ideas and formats for collaboration. I think the right-wing sites will be in danger of dying in the next few years, while the left wing will be able to evolve. But then, they never liked the idea of evolution, did they?