1. A method of providing information concerning use of a mobile device application, the method comprising: by a computer system that comprises one or more physical servers: providing user access to an electronic catalog, the electronic catalog providing functionality for identifying and downloading mobile device applications; receiving a submission of the mobile device application from a developer for incorporation into the electronic catalog; adding service code to the mobile device application received in the submission, the service code including functionality to report usage metric data, wherein adding the service code comprises identifying a predefined function of the mobile device application, and adding service code that causes execution of the predefined function to be reported in the usage metric data; distributing the mobile device application with the service code to mobile devices; receiving, from the mobile devices, usage metric data quantifying use of the mobile device application by the mobile, devices, the usage metric data generated by the mobile devices through measuring activity related to the use of the mobile device application, the usage metric data reported by the mobile devices by execution of the service code by the mobile devices; aggregating the usage metric data to produce aggregated metric data; based on the aggregated metric data, and additional aggregated metric data collected for other mobile device applications, determining a ranking of the mobile device application in terms of at least one of (1) average number of times launched, and (2) average amount of time spent using the mobile device application; and incorporating an indication of the ranking into a catalog page associated with the mobile device application, to thereby expose the ranking to users of the electronic catalog.