Smartphones aren't very “smart” without the software apps that give them their usability and versatility. Apps, like all software, need some degree of guidance, regulation, and measurement to ensure a user is receiving proper functionality and quality of service. This problem has existed in software engineering and software development from Day 1, and apps are no different. The void has led to a recent clamor for some way to vet apps and the app stores in which they will reside and be licensed. The guest editors of this special issue contend that this will be a huge problem for the mobile app market as it continues to grow; the articles they feature here attempt to address the challenges to come.