Normally in a web app i would put a font-family in the CSS something like this
"Â font-family: "Helvetica Neue", Arial, Helvetica, Geneva, sans-serif;"
This way i cover my bases as to whether the target browser can handle the various fonts and will fail gracefully if it is missing some.
However that are only a limited number of fonts on the iphone and presumably if you only specify one, say Helvetica, the iPhone will always have that font and use it. So i don’t really need a font-family. Do I?
A good reason given for at least adding the sans-serif font into the font-family is that Apple may change the iPhone or Safari in the future, so this would have some degree of future proofing.