Encouraging social experiences and interactions between nearby strangers has received both research and commercial interest over the past years. This paper focuses on two design qualities that have previously been found successful in this area: playfulness and progression. Employing the research through design approach, we explore these as design principles in so-called people-nearby applications. To evaluate how playfulness and progression contribute to encouragement of social interaction, we carried out a field trial with Next2You, a playful mobile application that automatically detects nearby users and exchanges user generated profile information. The results imply that the application features demonstrating playfulness and progression did contribute to encouragement of interaction between nearby strangers; however not as expected. The results provide a basis for reconsidering appropriate design decisions and methodological choices with respect to design and evaluation of people-nearby applications that aim to encourage interaction between strangers.