PhoneView uses the same methods of access used by iTunes, and it's subject to the same security constraints. If your iPhone is locked with a passcode, iTunes and PhoneView will not be able to access it on an unauthorized computer.
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Your home computer has security keys stored which allow you to sync or use PhoneView without having to enter your passcode. If connected to a stranger's computer, entering the passcode would be required before any data can be accessed.