Just read Anjo, Rogier and Lilia's presentation made yesterday at BlogTalk in Vienna called "Shared Conceptualization in Weblogs".
I wonder if it is possible to extract and match similar concepts expressed in several weblogs without the mediation of a common ontology. I can detect in Lilia's weblog some interesting "Knowledge Management" concepts for my work, but I will translate them in my own vocabulary (sometimes in French! "shared conceptualization" seems quite close to the "référentiel commun" I was talking about today in the CoP-1 meeting, and which I have hard time translating into English right now).
On the other hand, if Lilia does the same with my weblog (God forbid), it might make sense for us to sit together at some point in time and talk about our common view of the Knowledge Management field. We can then create a shared topic map (aka language) of common concepts to be used by each one of us to categorize our work so as to facilitate its reuse by the other. If there is a whole community of Knowledge Managers using the same topic map, it is even better. The point is that you need to agree on a common language first, which automatic clustering engines cannot do for you.