It doesn't seem to be a widespread issue -- so far I've heard of it happening on Telstra iPhone 4S units, but it may go further -- but it looks like the upgrade to iOS 5 may remove the personal hotspot feature entirely. Here's how to get it back. I've got to give thanks to Daniel Vooks (of Vooks.net) for passing this one along. Not just because it's useful information, but because restoring an iPhone 4S last night with a Telstra SIM in it made the same thing happen to me. Over the weekend, Daniel upgraded to iOS 5. Alongside all the shiny new features he noticed that something was missing; the personal hotspot feature that was present previously. He did something brave -- he phoned Telstra support to sort out the issue. Not always the smoothest procedure, but he's shared the details of what worked for him with me, which means none of the rest of us have to spend hours waiting on hold. Thanks (of a sort) to my own 4S doing the same thing last night, I can screenshot the procedure for you.
Hey, where's my hotspot gone?
Guess I'd better head into settings
And then network. In my case, all that was needed was to switch the hotspot back on, but Daniel's case was more severe.
The hotspot flag wasn't even there. Telstra advised him to reset the phone's carrier network settings.
Then reboot, reconnect to 3G and/or WiFi and head back into settings, then network. Personal hotspot should have reappeared.
So all you've got to do is switch it on.
I can now continue to hotspot away to my heart's content.