Tips: Easily Charge your iPhone on an unpaired MacJanuary 14, 2008
Sometimes it can be very annoying to have to go through the whole “this iPhone is synced with another computer…” business every time an iPhone is plugged in a Mac which is not paired with previously.
One quick way to prevent this from happening: just use set a passcode in your iPhone settings screen. Then, when you plug it in, iTunes will give you a single dialogue letting you know it can’t connect until you enter the code. Dismiss the dialogue, and you’ve got a charge-only setup.