One of the interesting elements about the modern web experience is that users are expected to be part of a community, and web site owners are expected to provide the infrastructure to support it. You can see that in a combination of different tools.

Blogs contain support for people to comment, and you'll often see the same people comment on the same post, and even have conversations through the comments on a single post to the point that you know the person that is posting based on their posts. We're seeing the same with other sites. del.icio.us, Shoutwire, digg and even older sites like Slashdot all work on the same principle.