Geoff Cohen of Coherence Engine was recently having a rant about a particularly useless site about the safety of a sugar substitute - and specifically, the problem that linking to the site just improves the site's page rank. This has, in turn, lead to some discussion about how people have tried and failed to build a business model around various web annotation systems, the various technological failure and why it's still important.

Seems to me that this is a problem that Google's page ranking system is tailor made to address. The very tech that they use to discriminate against enthusiastic bloggers and journal writters artifically elevating a site's page rank is the same tech that can be used to generate a page of search results which are discussion pages that link back to the site you're interested in. Just add a link to each search result along the lines of "See what people say about this site". Sort the page of sites that link to your target site favouring blogs, discussion boards and mailing lists as more likely to contain customer opinion, and you have an instant annotated web.