I'm sure someone will release an app that will let you tether via ad hoc networking... Anyway, here's a great article on Apple's target market: http://www.jkontherun.com/2008/06/smartphone-make.html
...So you other smartphone makers better smell the Applesauce and get things a lot easier to use. Not for the geeks but for the Aunt Sues out there. There are many, many more Aunt Sues than there are geeks and as the iPhone 3G is launched all over the world there will be millions and millions of Aunt Sues who will be able to get their hands on one. So you'd better get that super easy to use smartphone out pretty soon and get the word out to the Aunt Sues out there or you may end up sucking wind.