On the scalability issues of onboarding millions of LN mobile clients

ZmnSCPxj discusses the limitations of using opportunistic payment channels to pay for validation information in Bitcoin's Lightning Network. He argues that a light client may be defrauded by its direct peers and therefore cannot rely on them to forward payments to validate information. Thus, an alternative payment system, similar to watchtowers, would be more suitable. In this system, the validation-information-provider is prepaid and issues tokens that can be redeemed later. However, this system is not practical for opportunistic on-same-WiFi setups where a laptop is running a validation-information-provider-for-payment program on the same WiFi as a light-client mobile phone. ZmnSCPxj suggests that such a service should be built on top of watchtower service providers.