Why in the world does it matter? If Facebook wants to use the iOS sideloading scene to promote organ harvesting or whatever, we use that to sue them. From the outside-looking-in, it seems like another one of those hissy-fit scenarios where Apple's petty disagreement with other companies actively reduces the capability of their devices.
Sue them for what? Gathering user data that users gave an explicit permission to gather?
Previously, the app devs wouldn't be able to, for example, lock out the entire app from being used, just because you didn't give them permissions for something that isn't vital for the app to function (e.g., location tracking or photo gallery). App Store rules prohibit that behavior, and those apps get rejected.
Sideloading would allow FB and others to do that and more, since they won't need to follow App Store rules anymore. And I don't think there is anything illegal about them doing it.
