It seems to be gone now, but for a while, when I clicked on my AirPort icon to see what networks were up, one of the entries on the list was "Amanda's iPhone".

In as many years as there have been iPhones, I've never before seen one included in my networks list.

What was Amanda doing that nobody else has ever done?

went to settings and turned on Personal Hotspot?

You don't see it often because it's only going to show up while they have that on.
Most people turn that off when they're done using it. And they only need it when they need internet on their laptop or wifi-only iPad etc when they're out of range of someone else's wifi.

…and if someone else taps in to that connection they are burning Amanda's monthly data download allowance on her telco account.

those usually generate a one-time simple numeric password. I have yet to see one that lets you create an open wifi access point. At least they used a few brain cells developing that one.

Thanks for the insight. (The network was locked.)