Mobile psychological interventions are of growing interest, particularly for populations with little access to traditional mental health services. Optimum structural components of these interventions are unknown. In this study, twenty-one adolescents (age 13-17) with past two week depressive symptoms were recruited from the emergency department to participate in a semi-structured interview, to inform development of a text-message-based depression prevention intervention. Teens expressed conflict about intervention structure. Although trust and reliability were essential to sustain engagement, teens disagreed about how to best maintain reliability; whether the program should be "pushed" or "pulled"; and what the ideal degree of human interaction would be. These findings highlight the challenges in automating psychological interventions that are normally delivered face-to-face. Data indicate a broad desire for developing tailoring methods for system design (duration, frequency, and level of interactivity). The paper closes with thoughts about potential solutions to these structural issues for mobile psychological interventions.