What's exactly the reason I wroteThat is bad style in most cases.
In this case backup and access rights are not of relevance, because the user account usally has write permission to an usb stick or whatever he plugs in and such media are normally not touched by backup scripts.
But If you make you app "portable" you should think about how this can annoy users who install to hard disc the normal way. Maybe one can work around this by runtime checking somehow if the app is started in normal or portable mode.