tawawa.org has done some research into early blogs, making the argument that attributing the sources for links was the spark that ignited the blogging phenomenon:
The blogosphere arose on 24 April 1998. On that day Steve Bogart made the announcement that he was adopting Jorn Barger’s recent practice of attributing the source of the links he was posting to his weblog. Barger’s innovation of crediting the origin of his outbound pointers, adopted by Bogart first and by many others afterwards, infused an earlier, mostly dormant network with a dynamic it had previously lacked, turning the aspiration of a self-aware social medium into the reality of such a medium.
I’m very glad all of the old blog content is archived so that this sort of analysis can be performed. Both Jorn and Steve are still at it, on blogs and on Twitter.