When the Prisoner's Dilemma Ceases to Be a Dilemma: Rapid Visibility, Exclusion Costs, and the Collapse of Short-Term Rationality in Platform Environments

The Prisoner’s Dilemma has long been used to illustrate the tension between individual rationality and collective welfare. However, this model relies on implicit assumptions such as delayed visibility of defection, fixed participation, and the absence of rapid exclusion mechanisms. This paper argues that contemporary digital platform environments—particularly social media and content-sharing platforms—have structurally invalidated these assumptions. Through rapid behavioral visibility, predictive pattern detection, and low-cost exclusion, short-term defection strategies no longer yield even temporary advantages. As a result, the classical dilemma collapses: defection is no longer rational, and cooperation emerges not as a moral preference but as the only viable strategy. This paper synthesizes concepts from iterated games, reputation systems, evolutionary game theory, and platform governance to propose a phase shift from dilemma-based interaction to participant filtering. The findings suggest that recent changes in platform algorithms and monetization policies are best understood as rational responses to the breakdown of short-term strategic viability rather than as moral or ideological interventions. Keywords: Prisoner’s Dilemma, short-term rationality, platform governance, reputation systems, exclusion, social media algorithms