Establishing a grassroots innovation pipeline has come to the fore as strategy for nurturing innovation within large organizations. A key element of such pipelines is the use of an idea management system that enables and encourages community ideation on defined business problems. The value of these systems can be highly sensitive to design choices, as different designs may influence participation. We report the results of a case study examining the use of one particular idea management system and pipeline. We analyzed the content, interaction, and participation from three creativity challenges organized via the pipeline and conducted interviews with users to uncover motivations for participating and perceptions of the outcomes. Additional interviews were conducted with senior managers to learn about the objectives, successes, and unique nature of the pipeline. From the results, we formulate recommendations for improving the design of idea management systems and execution of the pipelines within organizations.