Wasn't Homejoy's problem the fact that once people found someone they trusted, they would just transact with them outside of Homejoy and, thus, not pay Homejoy

Wasn't Homejoy's problem the fact that once people found someone they trusted, they would just transact with them outside of Homejoy and, thus, not pay Homejoy the repeated commission they expected? By contrast, you can't get the benefit of Microsoft's Windows ecosystem, or Apple's app ecosystem, without first giving Microsoft/Apple the full amount of revenue they expect from you. In other words, a differentiated supplier / externalised network moat is only a moat if the vendor can get all its revenue upfront, or can reasonably ensure that the moat will keep customers locked in for a long time.