I was sceptical about this - where does the value come from? - until I read the part about mapping the social trust.

There is value in mapping these relationships. Trust enables lowering the cost of transacting. Low cost of transacting enables creation of powerful ecosystems.

It's the first proposal that I am aware of that introduces an economic incentive on an individual level for mapping trust. The system seems potentially very robust: 1) I add people I trust in order to increase the value of my coins 2) If I make a mistake and add an actor who turned out to be untrustworthy I am penalized by losing some value from my coins

Thanks to this dynamic, there is both an incentive to expand the network and eliminate bad actors on an individual level.