Touch screen phones would require clean hands, unless you want to constantly wipe them on your shirt. I have trouble keeping the BBerry with a keyboard clean; I can't imagine putting my grubby little fingers on a screen all the time to use the device.
It follows that iPhone users probably wash their hands more to keep their phones clean, yes? And with that, waa laa, less spread of illness. Watch and see. Bet someone studies it.
So, if I don't answer your "friend" request, don't take it personal. Just have other things I would rather do.