[jimbojohn]

An up-to-date iPhone is not trivial to jailbreak, especially if it isn't yours. Jailbreaking is a specific kind of rooting. It "ought" to be virtually impossible.

Then good luck hiding your trail, reassociating the Apple ID, hoping no apps broke due to the jailbreak (it's happened to me), keeping the device associated with the owner's iTunes, etc.

[aikinai]

There are times when jailbreaking an up-to-date iPhone is not possible, but right now the latest firmware can be rooted in a few minutes with a very simple program. It does not affect your Apple ID, iTunes association or anything other apps. It just gives you root access and installs the jailbroken app store from which you can install OpenSSH, etc.

I'm not sure if there are any trojans available, but if there were, you could easily install them and then either delete the jailbroken app store or just hide it from SpringBoard.

This process could easily be done in 10-15 minutes as long as you have physical access to the phone.