I've started commenting on blogs a lot more often and I'm finding it to be really fun. Many times the comments section of a blog post is more interesting and insightful than the blog post itself. And interacting with the blogger and other readers allows you to engage much more into the topic.
There's a web service called Disqus that runs the comments section of many popular blogs. Initially the idea of a web service for blog comments seemed silly to me but it's actually pretty cool (except that it doesn't work well on an iPad or mobile device). You can setup a Disqus account or simply log-in with Twitter or Facebook. Once your account is setup, you can build a profile and an 'about me' page and the service will track all of the comments you make across blogs that use Disqus. You can even "follow" commenters that interest you and be alerted whenever they comment. You can see my profile here.
Disqus is brilliant in that has formalized the interactions we have on blogs. It allows us to learn about the people we interact with and easily stay in touch with them over time. In many ways, it's really another social network...not that I needed to join another.
I could see Disqus being very useful for recruiting employees, consultants and partners. A blog community that focuses on your industry is a great place to find people that can help your organization. And Disqus allows you to interact with them, watch them communicate, understand how they think, learn more about them and get in touch.