Breaking my extended blog silence (I've been busy, you know, starting my full time job at Mozilla!) to tell you about the quagmire I went into when I tried to set up tethering on my iPhone.
So here's the story - with links that will help you avoid what happened to me.
I purchased and ADC membership so I could download and install the iPhone 3.0 SDK and OS. When Beta 5 came out I eagerly updated since my phone had been crashing regularly and went into restore mode. As soon as the 3.0b5 update went live on my phone, iTunes said it needed 8.2 to work so I downloaded the most recent version from ADC. This turned out to be 8.2b10(13) which disables the ability to change carrier settings and thus, to enable tethering if you didn't already do it before the update.
So - after many (failed!) attempts to go back to 3.0b3 and 3.0b4 so that I could use iTunes 8.1 - I did eventually (10 hours and many blog tips later) work out my tethering issues with this extremely simple set of steps:
Simple Steps to restoring tethering:
Download: iTunes 8.2b7(10) http://thepiratebay.org/torrent/4874487/
* Delete iTunes 8.2b10(13) from your computer, install the older version - as the torrent description points out, it says that it installs as an 8.1.1 but it is in fact 8.2.
* When you connect your phone in iTunes, Option-click the “Check for Updates” and pick the.ipcc file for your carrier (from the carriers patch you downloaded). It will update the carrier settings.
* Reboot (NOT RESPRING) the phone. You can now tether over USB or BlueTooth (unless you have a new Mac Unibody Mac where apparently the Bluetooth stack is broken and so you're relegated to only sharing via USB).
To activate tethering, go to “Settings->General->Network->Internet Tethering”. The first time you do so it may say “Contact Rogers to enable this feature”, but a few second later it should allow you to enable it. If not, restart the phone again.
Thanks to many blogs out there but more specifically to Adam Mcnamara where the bulk of the steps are from.