One of the most interesting things to come out of the Q&A session at the iPhone OS 3.0 launch was a statement that the latest iPhone touch contains Bluetooth radio hardware that Apple can enable with a firmware update. If you missed it it's at 11:43 AM in gdgt.com's live launch coverage.
I doubt that that Apple would ever enable the dial up networking profile. But if they did you could tether an iTouch to a cheap feature phone on the network of your choice. As a cheapskate who is unimpressed with AT&T's pricing and 3G reliability I would definitely do that.