Social media platforms are transforming individuals from passive receivers as in traditional one-way communication channels to active senders who react to and disseminate information easily. However, such feature breeds a wide spreading of unverified information online, i.e., rumor. Previous research pointed out the duality of social media that it can serve as a potential tool for social reporting by leveraging users' collective intelligence, but it could also become a collective rumor mill. We propose that repost amount will positively influence the survival time of rumor, which we use to indicate the effectiveness of social reporting system. The preliminary results support our hypothesis and social contagion theory are adopted to explain the mechanism. We elaborate on the potential contribution and future research plan as well.