Strip Invisible Metadata
When a service requires a user to import data from external sources (eg. pictures, tweets, documents) different types of metadata may be transmitted. Users may not be aware of the metadata as it can be automatically generated or not directly visible. Services might be inadvertently responsible for exposing private metadata, or going against users' expectations.
Users are not always fully aware of the various kinds of metadata attached to files and web resources they share with online services. Much of this data is automatically generated, or not directly visible to users during their interactions. This can create situations where, even though users share information explicitly with services, they may be surprised to find this data being revealed. In certain cases where the data is legally protected, the service could be held responsible for any leakage of sensitive information.
How should services that need users to share data and upload files treat additional metadata attached with files? In case of uploading documents and images, which parts of the metadata can be treated as explicitly shared information.
Stripping all metadata that is not directly visible during upload time, or during the use of the service can help protect services from leaks and liabilities. Even in cases where the information is not legally protected, the service can protect themselves from surprising their users and thus alienating them.
Additionally when users share data with services, they can be presented
with a preview of the data obtained by the service, including any
[[Preview Shared Data]]. This allows users to be more aware
of information that they are sharing with the services, and in many
cases with other entities on the Internet.
To summarize: user metadata that can not be made visible to users clearly should be stripped to avoid overstepping the users' expectations.
Twitter.com removes EXIF data from images uploaded to their image sharing service. Previously there have been many breaches of personal location by using EXIF data shared by image sharing services.
In certain cases services might build features based on metadata, or the metadata sharing could be an important part of the community of users. Flickr.com allows users to hide their EXIF data from public display, and also provides an interface for users to easily see whether they are sharing location as part of uploading their images.
TODO: add screenshots