I recall seeing the internet tethering options in my iPhone 3.0 settings recently. I turned them off to save power by not using Bluetooth.
Now they're gone! And I want to tether but don't know how to re-appear them :P
https://cdn.geekzone.co.nz/imagessubs/blog903ad56cd69c3c4d85274e27c13a9c45.jpg - my network settings screen, missing tethering button
https://cdn.geekzone.co.nz/imagessubs/blogeb6916288896922edde42ce91d0f76f3.jpg - my hardware / software versions etc