I just saw an interesting post from Wired's Epicenter blog discussing a new approach to user comments on blogs. The author points out that since social media tools like Facebook, Twitter, FriendFeed, etc. pull in blog content and then allow for commentary to be posted about it, the feedback tends to come from smaller, more closed groups.
In order to promote a wider, and perhaps more critical, pool of commentary, Jim Jeffers has started a project called Encouraged Commentary, which allows the user to highlight any text in order to be prompted with a 'respond' option. By clicking 'respond,' the user will be given a comment message box with their selection already formatted. This way, a user can respond with relevant comments (ideally), and not just, "nice post." Check it out.
I think the idea is solid, I just wonder how they'll get people to start using it if most are already used to pulling blog content into other sites?