Russell Shaw at The Industry Standard has a clue:

"Google is the leader in the Web-search space, but is mediocre at best in the Blog-tracking space. It takes days, if at all, for some of my various blog posts to come up in a Google search.

Technorati is, at least to me, the leader in the Blog-tracking space. As I type this, (around 2 p.m. Pacific Time on Thurs., 1/13) they are watching 5,986,975 blogs, and tracking 766,620,835 links."

Mhh very smart that is probably Technorati's only business model? Why do you buy somebody without revenues and relatively simply teh copy technology? Let's see what happens...