Firms increasingly engage customers in idea generation (or ideation) to sustain their competitive advantages. Drawing from social interaction literature, this study adopts a social network perspective to investigate empirically how the characteristics (i.e., direction, size, and strength) of customers' online peer-to-peer (P2P) and peer-to-firm (P2F) interactions, moderated by customers' past efforts to post ideas (i.e., past ideation participation), influence their likelihood of generating ideas in an idea crowdsourcing community. With four years of data from a popular online crowdsourcing site, this study demonstrates the significant impacts of P2P and P2F online interactions on customers' likelihood of subsequent idea generation. In particular, a potential double-edged sword of past ideation participation emerges: A high level of past ideation participation strengthens (weakens) the impact of P2F (P2P) interactions on customers' subsequent idea generation. These findings suggest implications for how firms can cultivate customers' online social interactions with peers and firms and enhance their capabilities for capturing the wisdom of the crowd.