Commercial quiz apps show characteristics, which could contribute to a promising game-based learning tool. Among these characteristics are huge popularity, easy accessibility and adaptivity to any content domain. We used the commercial quiz app QuizUp in an explorative study to clarify acceptance and requirements for the usage of these apps for educational purposes. We developed a topic-specific question corpus. Over a period of 12 days four topic affine students used QuizUp regularly and focused on learning. We observed them in three common gaming sessions. Furthermore, three interviews and a questionnaire were conducted. A main observation has been a self-reported decrease of motivation after a phase of curiosity. In general, we conclude that successful usage of such a quiz app requires a purposeful integration in an educational setting to ensure its continuous use. Additionally, we point to a set of further relevant research topics.