Online health message boards have become popular, as users not only gain information from other users but also share their own experiences. However, as with most venues of user-generated content, there is need to constantly make quality evaluations as one sifts through enormous amounts of content. Can interface cues, conveying (1) pedigree of users posting content and (2) popularity of the posted content, help new users efficiently make credibility assessments? Furthermore, can the assignment of these same cues to their own posts serve to motivate content generation on their part? These questions were investigated in a 2-session between-subjects experiment (N = 99) with a prototype of a message-board that experimentally varied interface cues, and found that popularity indicators are more influential than pedigree indicators for both evaluation of existing content and contribution of new content. Findings also suggest theoretical mechanisms - involving such concepts as perceived authority, bandwagon effects, sense of agency and sense of community - by which cues affect user experience, providing rich implications for designing and deploying interface cues.