Comment by aylmao

Hm, the catch here is something like this could happen:

  +--------------+        +----------+        +--------------+
  |              |        |          |        |              |
  | other server |        |  Server  |        | other server |
  |              |        |          |        |              |
  +-------+------+        +----+-----+        +-------+------+
          ^                    |                      ^
          |                    |                      |
          |               http request                |
          |               containing user             | 
          |               data for UI                 |
    http request made          |               rouge http request
    with a legit purpose       |               sending the user data
    say fetching assets        v               to some other server
          |            +-------+-------+              |
          |            |               |              |
          +------------+  mobile app   +--------------+
                       |               |
                       +---------------+

And there is really no way of knowing which requests are for legit app purposes and which would be leaking data. Now, you could require that the mobile app make no requests to any service but Facebook, which brings two questions:

1. can facebook do this? Apple could; they approve apps and get the binary/manifest before the app is released. But how could Facebook enforce this?

2. would developers be ok with this? Relying 100% on facebook?

It is an option, I'm not saying it's infeasible. An interesting idea for sure, thanks for sharing!