This is right now more a reminder to people who want to handle invocations by other apps.

Situation:
If iOS invokes the app with an incoming file, the QDesktopServices registered handler for file:// will be invoked (see https://qt.gitorious.org/qt/qtbase/commit/c5b19f252188a01dd7b12090f4776420e3714000 ), since incoming files will be in

file://localhost/private/var/mobile/Applications/[bundleid]/Documents/Inbox/

Registering your own file:// handler then however breaks invoking outgoing file:// URLs
since our own handler will be invoked. (whatever the default for iOS is, maybe it's not implemented yet anyway)

Workaround: Use UIDocumentInteractionController directly if you want to do outgoing calls.