Dave wants a tool that can show you how connected two weblogs are to each other, and indicates what the traffic looks like between them. I think he’s right that the second is impossible for a centralized search engine… but what about a distributed referral collection app?
As for the first, the Netscan project at Microsoft Research does something similar for newsgroups by tracing cross-postings and provides visualization. Blogdex traces links from blog to blog. It should be possible to apply the visualization and connectability capabilities from Netscan to the data that Blogdex collects.
If someone does this, I want credit on the thesis. 🙂