1.       What looks good on a 15+” screen looks crammed and busy on a 3.5” screen.

2.       What runs sufficiently fast on a dual core processor may become slow on a ARM processor.

3.       What flows through broadband quickly doesn’t flow nearly as well in 3G or even 4G.

4.       The experience of using a mouse and a large keyboard is quite different from using a touch screen, roller ball or joystick.

5.       What makes for an acceptable and relevant user experience when browsing the web leisurely at a desk may become completely unacceptable and useless while marching down a sidewalk.