> The more promises we make to each other, the more likely we are to be in a chain where somebody cannot keep their promise, which means that we are vulnerable

> The more promises we make to each other, the more likely we are to be in a chain where somebody cannot keep their promise, which means that we are vulnerable to a cascade of failed promises. You can think of a promise as an edge between nodes in a graph. A failure cascade occurs when removing a single edge causes many nodes to become unreachable. Whether adding edges increases that change depends entirely on the topology of the graph. A long linear chain increases the risk. (But you have to implicitly create new nodes—new lenders—in order to maintain that topology while adding edges.) But if you just add edges without increasing nodes, the result is that the graph becomes more connected and thus more resilient to edge loss. In other words, if you owe me $100 and don't pay, I'm out $100. But if five people owe me $20 and one doesn't pay, I still get $80 back.