imagine something like linkedin's 'how are you connected to this person' - except instead of 'we worked together' the edges are all of the form 'i trust this person to this extent.'
you take a bunch of statements of this form (node X trusts node Y with level 0.4), all signed by private keys. if you meet someone else, you can see all of the trust paths from you to them, to decide how much you trust them, and to what extent.
then, instead of having to personally know someone else personally, i can say 'there are 300 paths from me to this woman. 250 of them are strictly positive with trust levels over 0.7 which is my default threshold for comfort. all of the negative ones turn negative over two hops from me, and only three are intensely negative. i already had weak trust levels for intermediary nodes between myself and the negative inbound edges to her. she's fine, and i have more confidence in my negative assessment of those intermediary nodes.'
this could be huge. it would let us have more trust in strangers, and it would let us do things like this:
- 'this lawyer has 50 inbound links from people i'm relatively close to, that all rated him as an asshole. i wont work with him'
- 'this guy i'm serving at the restaurant has 30 level-4 links out who've said he helped them when they didn't offer anythign in return. i'll service him better than this other guy over where who's been rated as rude and elitist by some closer level links to me'
- lets look at the yelp reviews of these restaurants, weighted by the trust scores i give users who've left the reviews. hmm, all of these reviews are from identities i only have a few paths to, with all of those paths passing through my SEO friend, who i thought might be black hat. drop this guy's trust level to negative and mark all of those reviews as untrusted by me. don't want my friends to waste their time with that.