Under explicit consent of the people putting the data in. All this needs is a nice informative screen on how the data will be used and that it will be publicly

Under explicit consent of the people putting the data in. All this needs is a nice informative screen on how the data will be used and that it will be publicly available, which may mean being processed by other registered users and unknown third parties. The networks will not be able to process the data in other ways than making it available. If you break someone's privacy laws you will be liable directly. Probably also a note that data on this network cannot be completely deleted for specific technical reasons.