As social media and virtual communities increase in popularity, the spread of word of mouth becomes easier, challenging firms to measure and manage the success of marketing initiatives in online community environments. This research examines how consumers react to firms' active participation in consumer-to-consumer conversations in an online community setting. The authors develop a tailored community-matched measure of consumer reaction (consumer sentiment) and analyze more than 115,000 consumer posts from ten online forums with active firm participation. The results indicate that consumers show diminishing returns to active firm engagement, which, at very high levels, can undermine consumer sentiment. Further subgroup analyses by conversation type indicate that these relationships hold for conversations that address consumers' functional needs but do not hold for conversations that address social needs. Finally, the results show diminishing returns to firm engagement for consumers primarily interested in product-related support but show no relationship for consumers primarily interested in inspiration and entertainment. These findings provide insights for marketing performance measurement and resource allocation in online communities.