I've always found it annoying when I saw the same for BlackBerrys. It always conjured up images of marketing types striding purposefuilly through airports. I've decided to up my annoyance level for iPhones.
Is there any conceivable reason why I should care about the specific device from which a message was sent?
The only justification I can think of (other than misplaced viral marketing) is that the sender wants to explain the brief & cursory messages that typing on such a device requires.
If this is the reason, would not 'Sent from a device with a crappy keyboard' achieve the same?
And wouldn't Apple want this reality downplayed rather than hilited?