Say you read a lot of blogs and you're a compulsive commentor (commentator?) on said blogs. You start having difficulty keeping track of which entries you've vastly improved by adding your witty or poignant prose in the comments section. You may be in need of a tool like coComment.
Here's another, from the same blog, next post:
Let's face it. Blogs aren't a conversation. They're a soliloquy. It's just that, sometimes, the audience yells back at the actor.
We have a conflicted view in the blogosphere over this. On blogs with a low flow of comments, they tend to be useful - but as the volume of comments increases, the ratio of signal to noise just gets worse - just as it did on Usenet, Slashdot, and Digg. Pretty much, it's just the way online communities operate.