One subject you could explore is how the metrics given by Facebook affects the perception of a "successful" app. The primary metric for applications is daily a

One subject you could explore is how the metrics given by Facebook affects the perception of a "successful" app. The primary metric for applications is daily active users, while Facebook itself defines an "active" user as someone who logs in at least once a month - I always thought that distinction is interesting. The secondary metric are total installs. Things like repeat users, page views, pages/visit aren't as used. This has the strange effect that large quiz apps - which tend to rise and fall in a matter of about a month - are usually seen as more "successful" than applications with a steady returning user base.