If you really wanted to show off that you had an iPhone you'd probably at least want to say: "Sent from my White iPhone 4, 32GB with Retina Display" ;-) But se

If you really wanted to show off that you had an iPhone you'd probably at least want to say: "Sent from my White iPhone 4, 32GB with Retina Display" ;-) But seriously, I imagine most people who have this signature in their mobile emails have no idea how/where to change or disable it. The other reasons you cite are legitimate possibilities, but probably to a much lesser extent.