Hyperlinks to establish referential identity and so common ground in blogs...
A seminal work in the communication literature that we're looking at in our doctoral seminar is the famous Clark and Brennan (1993) piece on common ground. It discusses how common ground is established in conversation and also reviews how features of different communications channels help/constrain grounding and how common ground can be different when communicating over different channels. For example, e-mail is reviewable and revisable, but not cotemporal or audible (in the traditional view). Common ground is established via the least collaborative effort required for the channel.
So this seems obvious, but it's worth making the connection to the literature.
Referential identity is "the mutual belief that addressees have correctly identified a referrant" (Clark & Brennan, 1993, p227). In f2f conversation it is frequently done by actually pointing to a physical object (indicative gestures) -- this desk here, that pen there, go left down there. This is something that is difficult even in video conferencing because of the wierdness of framing (more on this in Olson & Olson 2000), etc. In blogs, we refer very specifically to points in text by linking. The formulation and production costs are higher (actually finding and coding in the link) but the collaborative effort is less than without the link because the understanding is quicker - especially for one who is familiar with the referrant but needs to be reminded.
I think the blogosphere has talked more about links establishing common ground in that they establish a common history and context. I link to librarians therefore I have an affinity towards librarians and/or I am one. More of placeing a person in their discipline via their blogroll and linking... but blogs are conversation...
Maybe this is all obvious.... ah well, I've spent the time typing it so I'll post :)
References
Clarke, H. H., & Brennan, S. E. (1993). Grounding in communication. In R. M. Baecker (Ed.), Readings in groupware and computer-supported cooperative work: Assisting human-human collaboration (pp. 222-233). San Mateo, CA: Morgan Kaufmann Publishers.
Olson, G. M., & Olson, J. S. (2000). Distance matters. Human-Computer Interaction, 15(2-3), 139-178. (eprint available via CREW at http://www.crew.umich.edu/publications/00-04.pdf )