What are "On Demand" and "Public Access Wifi" wireless networks ?

While browsing a list of wireless networks on your Windows PC, you can see three different kinds of signals, "secured", "unsecured" and "On Demand". While the first two types are self-explanatory, the third type is often a source of confusion. To further obscure the issue, those "on-demand" networks are often named "Public Access WiFi", and you can connect to them, however, they do not offer actual Internet access.

By "on-demand", the wireless manager refers to an "Ad Hoc" connection - a direct wireless connection between computers with no central "access point" involved.

There is a bug in some versions of Windows XP, where if the computer tries to connect to one of those "ad-hoc" networks, then their computer perpetually broadcasts the address of that network to all other nearby devices as an available ad-hoc network, even months/years later.

The majority of such Ad-Hoc networks provide no Internet connectivity, and they're often the results of laptops perpetually broadcasting the address of an old ad-hoc access point that provided public access Wi-Fi somewhere, sometime in the past.

To summarize:
1. They are ad hoc networks, making it unlikely that a device with an Internet connection participates.
2. "Public Access Wifi" and similar SSIDs are not in fact public access wifi hotspots. They're merely created by misconfigured Windows software. When you connect to one, you are most likely connecting to someone's laptop, not to a piece of equipment intended for Internet access.