I spent some time today exploring Technorati. The suggestion to try searching for "School Library Learning 2.0" different ways was certainly a good one - the results were different with each type of search. One of the challenges I face with the students I teach is that so many of them try just one search of our catalog, databases, or anything we recommend, and give up when they don't get immediate results. For those students who will listen, I think one of the best pieces of advice I give them is that, if they want good results, they have to be detectives and do at least three or four different searches trying different terms and methods. I know I've wandered here a bit, but I think the advice holds with Technorati - to use it effectively to find something, you have to be prepared to do a variety of searches.
I have liked learning about a variety of tools that use tagging. I can't really see any disadvantage to tags, just advantages. To me, they seem like the current equivalent of catalogers' subject headings, but more free form. I like having books organized by Dewey, but you really need the subject headings or keywords you get in the catalog to make them accessible in a variety of ways. Likewise, the tags used by tools like Technorati and del.icio.us allow for finding sources a variety of ways.
I don't see becoming a regular user of Technorait right now (I already subscribe to more blogs than I really have time to read), but I like knowing about a tool I can use to find blogs if I ever want one on a specific subject. (And, I will remember to search a variety of ways :) ).