The opt-in sharing model has a simple premise. By default, an application with this model will not share information about the user publicly or with other users that he may be connected to. To begin sharing information, the user has to manually enable that feature through the application.
A good example of this type of model is a location-based application. Before using your physical location, the application will request that you allow it to do so. If you allow the application to track your location, you are opting in.
The opt-in sharing model is a clear benefit for the user, not the application or network requesting the information. The user will need to either modify his sharing settings manually or enable them through prompts that the service provides. This protects the user by forcing him to understand exactly what he’ll be sharing through the application before he commits.
A social service’s life-blood is having that sharing mechanism enabled. It increases user interaction, time on site, and adoption through community awareness. But since many users do not enable the full gamut of social sharing features, the service’s reach is often limited and growth occurs at a slower rate.
Many services that implement this model prompt the user to allow the service to use and share his information, because some users never venture into the service’s privacy and sharing settings. By prompting the user, the service forces him to make a choice one way or another. ...