I think it has shown some use in content categorization and journalism. The rise in anime review blogs has helped me a lot in finding new, interesting shows. For discussion it's not very practical. Like someone else said, blogs are more about people talking to themselves than conversing with others.

One thing I find odd about it is this new proof of identification system they've got floating around(I forget the name). It's essentially an analoge to tripcodes, in that they can provide verification of comment entries coming from one unique source across multiple blogs/websites. The idea I presume being that registered impostor accounts on another site would be more easily distinguished. The system is somehow tied into ownership of a website, and appears really cumbersome to me from what little I've read of it. It seems to me like a ridiculous amount of effort just so someone else doesn't use your name when commenting on another nobody's blog entry. This probably says a lot about the difference in the anonymous and "social" mindsets, but I don't think I can articulate it properly.