Trust/Reputation in Search

I've been wondering whether reputation can be conveyed in any other way in search algorithms than Google's PageLink algorithm (which seems to me to be a measure of popularity - albeit in a network sense - rather than of reputation). I was reading an article in the ASIST Journal called "When Documents Deceive" by Clifford A. Lynch on the bus home, and came across the phrase:

"The question of formalizing and recording expectations...[of] trust in behavior [is] very poorly explored. There are a number of avanues: certification or rating services that might be consulted, or webs of individuals vouching for behaviour of others"

I'd been pondering whether it might be possible (particularly in an intranet) to modify a search engine so that when a user rates a page, he or she can also see in his/her search results how people like him/herself have rated the pages and/or how people he or she trusts rated the pages. This might seem a bit daft, but I was wondering whether, a bit like FOAF, a search engine could have a "who do you trust?" section, where you log-in, and then identify other people on a database whose opinion you trust. Search results might gain extra weighting within the overall results based on their "reputation" rating 9where the results would be specific to your trust network). I suppose the problem is placing the burden on users of registering and keeping their "trust networks" up to date, and the fact that it would become a very large database, but that detail could be ironed out by brains greater than my own.