How do consumers hold sellers accountable and enforce market norms? This Article contributes to our understanding of consumer markets in three ways. First, the Article identifies the role of a small subset of consumers—the titular “nudniks”—as engines of market discipline. Nudniks are those who call to complain, speak with managers, post online reviews, and file lawsuits. Typified by an idiosyncratic utility function and certain unique personality traits, nudniks pursue action where most consumers remain passive. Although derided in courtrooms and the court of public opinion, we show that nudniks can solve consumer collective action problems, leading to broad market improvements.

Second, the Article spotlights a disconcerting development: sellers’ growing usage of big data and predictive analytics allows them to identify specific consumers as potential nudniks and then disarm or avoid selling to them before they can draw attention to sellers’ misconduct. The Article therefore captures an understudied problem with big data tools: sellers can use these tools to shield themselves from market accountability.

Finally, the Article evaluates a menu of legal strategies that would preserve the benefits of nudnik-based activism in light of these technological developments. In the process, we revisit the conventional wisdom on the desirability of form contracts, mandatory arbitration clauses, defamation law, and standing doctrines.