Contemporary culture is characterized by individual and societal efforts to limit exposure to risk. Paradoxically, many consumers actively pursue high-risk consumption experiences. High-risk consumption, coupled with a lack of consumption-orientated information, amplifies consumer vulnerability. However, consumer-to-consumer information sharing can help reduce unwarranted risk and enhance consumption context control. This study investigates the ecstasy "market maven crowd": an online community anonymously bound by acts of collective market mavenism intended to address the void of market information and reduce the risks thereof. Acts of collective market mavenism include the assimilation and dissemination of scientific ecstasy pill content reports and personal ecstasy consumption tales. The diffusion of market-orientated information provides consumers with an opportunity to identify, and avert, the serious health risks intrinsic to ecstasy consumption and assert consumption context control. Collaborative market mavenism fosters market policing, which enhances the safety structures of the unregulated ecstasy market. This study contributes to marketing and consumer research by developing an understanding of how consumers collectively adapt to risk online; displaying market mavenism as an innovative framework to examine online consumer-to-consumer information sharing; showing how Internet technologies facilitate the emergence of market maven crowds; and providing marketers with guidelines for approaching market maven crowds. Finally, the author discusses the societal implications arising and suggests directions for future research. © 2015 Wiley Periodicals, Inc.Advances in technology are providing increasing opportunities for consumers to interact and relay a range of practical market-orientated information (