五边网络效应，基本牢不可破
在 Visa 一集的分析环节，David Rosenthal 认为 Visa 连接持卡人、商户、发卡行、收单行等多方，是罕见的「五边网络」：边越多越难搭起来，但一旦建成就被牢牢锁定。Ben Gilbert 补充了空头视角：自从银行可以同时发 Visa 和万事达卡，两家几乎没有转换成本，银行合同到期就比价，谁条件好选谁。
I think this whole story that we told of how incredibly freaking hard and unlikely it was that this happened means that you have a five-sided network effect business, and it's basically unbreakable.