Researchers frequently express frustration when confronted with data management plan (DMP) requirements, particularly when drafting or completing a grant application. This sense of annoyance is further fueled by a too-common view that the DMP is yet another hurdle that researchers need to confront during the grant writing process. Once researchers and students understand the purpose and utility of DMPs, however, many of these reservations and frustrations subside. The purpose of this exercise is to demonstrate the importance of DMPs by giving examples of large research projects that suffer due to poor data management planning. Each case provides examples of otherwise well-organized projects in which users suffered because long-term data use and access were not considered. In each case, a DMP would have identified and remedied the issues. While these examples do not address all the ways a project may suffer from insufficient data planning, they illustrate how the lack of a DMP can damage even a well-designed and well-executed research project.