Don also mentioned auto-population of blogrolls, which is something that Phil Pearson has been experimenting with and I've been commenting on. My view is that the "blogroll" can be extended to incorporate not only links to weblogs (people), but links to topics and conversations (weblog comments). Later on you could add other chunks of microcontent too - e.g. reviews, Wiki threads.
Blogrolls are usually files in an opml format and they are made up of links to other weblogs - i.e. links to people. Blogrolls are usually attached to a weblog's menu, along with other links, and they help foster a sense of community amongst bloggers. This is fine and noble, but I also want to link to topics that interest me and I want to track conversations. That's what the Two-Way Web is all about after all - publishing and subscribing. So why not extend the blogroll so that it is not just a compilation of links to people, but links to topics and conversations too.
Phil Pearson got it spot on when he said "a blogroll is a list of lists of links". The easy part is subscribing to people and topics. These are mostly static links, so you could add them manually to your blogroll.opml file. The hard part is adding conversations to your blogroll, because this is dynamic - conversations have a short shelf-life and eventually die out. And new conversations potentially pop up whenever a blogger posts a new weblog entry. Because conversations constantly change, you want to be able to add (and delete) them from your blogroll easily and preferably at the click of a button.
If the conversation is on a Wiki, then it would be good to be able to "subscribe" to that conversation from within the Wiki - and your blogroll automatically updates. Or alternatively, there could be a web frontend for your blogroll that allows you to easily add the Wiki page to your blogroll.