I suppose we could build a system that looks at all the posts on a topic from a tightly proscribed white list (there are many services that do this) but that loses much of the emergent serendipity of the blogosphere and excludes everyone except for a proscribed static elite. That’s neither fair nor interesting nor scalable. We're interested in what the whole blogosphere has to say on a topic. But to find the interesting relevant stuff we want to give a little more weight to bloggers that are revealed to be authoritative in a subject (not just because they say so in a tag, but because we observe many other topical bloggers linking to them in a democratic vote of editorial goodness).
I always saw TailRank as filling this space (perhaps not as elegantly as they could). The weird thing is that while Technorati is claiming to use no restrictions in terms of where they find links, the measure of attention that their highly rated stories achieve is amazingly low. Right now, the top news story has 1 link (Attention ). This indicates a more complex algorithm (or very light data rates), and the problem with complex algorithms is that users don't always follow why they are seeing something popping up at the top of the list. My feeling is that the solution to this problem is to discard the list for something with more dimensions to it.
Update: Well, that just shows my ignorance (or does it show an interface problem?) The attention score is not the number of inlinks found but, um, something else. There is an explanation here:
Technorati measures Attention by calculating a weighted rank based on time, number of links, rate of new links, Technorati Authority, and the Technorati Authority of linking blogs. Attention changes over time, so something that was getting a lot of attention this morning may be much less interesting later in the day. A Technorati attention-based view allows you to concentrate on those items that are gaining the most attention now, even when they were created hours ago.
Though I don't find it very clear. Attention might be a rank, in which case '1' is good. However, the story that I'm looking at right now has Attention  and 1 'attention link'. Confusing.