Although companies use crowdsourcing more and more to fill their innovation pipeline, it is not so easy to get people to submit their ideas to online innovation platforms. Our data from an online panel reveal that 65% of the contributors do not come back more than twice, and that most of the rest quit after a few tries. This kind of user churn is endemic to online social platforms — on Twitter, for example, a majority of users become inactive over time — and crowdsourcing is no exception. In a way, this turnover is even worse than ordinary customer churn: When a customer defects, a firm knows the value of what it’s lost, but there is no telling how valuable the ideas not submitted might have been.