Blogs adding to knowledge fragmentation?

Continuing my rambles on RSS, I've been vaguely worried recently that RSS-based weblogs add yet another level of fragmentation to the information store that is the internet.

Once upon a time there was Usenet, which was one of my primary knowledge resources. The advent of Deja News (now Google Groups) was a big leap in being able to tap into other people's expertise. Now I monitor mailing lists, RSS feeds, web-based forums not to mention instant messaging logs. It worries me that I often search Google Groups and get invaluable information, yet rarely contribute because of the low signal-to-noise ratio. How do I search the information sources that I now contribute to?