Apple released iPhone software 2.0.1 yesterday, an update to the original software that comes with 
the iPhone 3G. Apple isn’t saying why the update is needed at this time, only that the new software fixes bugs that have troubled the mobile device. I suppose it is only natural to want to keep such problems as secret as long as possible, due to potentially bad publicity or security risks bugs can cause.
Currently, the 259 MB software package can only be installed by connecting the iPhone to a computer and downloading through iTunes. There is no mention of why the procedure can’t be conducted over a user’s carrier network.
I don’t think downloading 259MB even over 3G would be ideal, and it would eat into many of the 1GB data plans. All those iPhones on EDGE wouldn’t manage 259MB either. Plus every “legit” iPhone owner has tethered their iPhone to iTunes at least once.