I would challenge the assertion that what The Economist is doing isn’t different from other publications. After receiving your comment, I did a quick search of the websites of comparable publications in the U.S. Neither Time nor Newsweek permits direct commenting on the letters of other readers, and U.S. News & World Report doesn’t post letters at all. On the upside, Time does offer social bookmarking of letters on Digg and other news sites, something that The Economist should consider going forward.

From an association point of view, however, the key point is not that what The Economist is doing is “new” in absolute terms, but that it demonstrates an easy and straightforward way to apply social media to publications that has the potential to create considerable new value for readers.

This approach doesn’t seem all that different from posting letters to the editor (almost all of which are received via e-mail these days, in my experience) to the magazine Web site, which many magazines already do. Maybe I need to poke around a bit more, but I’m not seeing this as anything terribly new.