[SketchySeaBeast]

Fasting and training are both conscious deliberate choices - how will you frame the loss of privacy in such a manner that it can be agreed to with the same degree of intention? Most people have no idea and don't understand - if you wanna go with the "opt in" solution, you're going to have to make a compelling argument that the people making the decisions are educated enough to make them.

[diminoten]

The same way a trainer or doctor frames the health risks involved; you explain it and hope people are listening.

Signing in via Facebook is also a deliberate choice.