Mary Hodder at Napsterization digs into the same issues I have been bumping against regarding Technorati's model of link counts:

Technorati also only counts links and sites from blogs that have a link on the front page. Therefore, if a bloggers blogs, which bloggers tend to do, their old posts scroll off the front pages and therefore the links in those old posts go off the Technorati count at the same time. Blogroll links stay in the counts because they are permanently on the front pages of blogs, but if a blogger's post links to another blog, that link only gets counted so long as it's on the linking blog's top home page.

Bloglines on the other hand, gives a total link count, for all Blogline's history. If a blogger is linked to 10 times, in the history of Bloglines aggregation of links, those links count as ten, towards Dave's Bloglines total. Bloglines doesn't give a base count of sources doing the linking. Also, Bloglines shows you everything since they started tracking blogs, so Dave's first link goes back to a post on August 22 2002. Technorati would age that post off their link counts, since that blog no longer shows the post on the front page (it long ago scrolled off the page). However, I wasn't able to look at Dave's first link on Technorati, because the service kept returning error messages about high search volumes, so I can't compare their first result to Blogline's first result.

Mary intends a multipart series on this and related issues: this one is on link counts, later ones are key word search, subscription (watchlist) search, spam, and special services.

Personally, I think a number of us are being poked into asking these questions becuase the growth of the blogosphere is leading to a breakdown in services -- like Technorati -- that we have come to rely on and, simultaneously, increasing the importance and value of these results.