Hacker News Reader

They aren't enabled by default.

"requires the user to have unlocked their device and agreed to trust another computer"

and

"For users who have enabled iTunes Wi-Fi Sync on a trusted computer"

They absolutely are enabled by default, running as active daemons which cannot be disabled by the device owner.

The circumstances by which they may be accessed include user agreement to "trust another computer", but may not be limited to that.

Because DROPOUTJEEP.