The picture has become somewhat confused as service providers started using WiFi to deliver services for which it was not originally designed. The two major examples of this are wireless ISPs and city-wide WiFi mesh networks.
One business that grew out of WiFi was the Wireless ISP (WISP). This is an idea of selling an Internet access service using wireless LAN technology and a shared Internet connection in a public location designated as a hot spot.
From a technical standpoint, access to the service is limited based on the transmission range of the WLAN technology. You have to be in the hot spot (i.e. within 100m of the access point) to use it. From a business standpoint, users either subscribe to a particular carrier's service for a monthly fee or access the service on a demand basis at a fee per hour. While the monthly fee basis is most cost effective, there are few intercarrier access arrangements, so you have to be in a hot spot operated by your carrier in order to access your service.
To address the limited range, vendors like Mesh Networks and Tropos Networks have developed mesh network capabilities using WiFi's radio technology.
The idea of a radio mesh network is that messages can be relayed through a number of access points to a central network control station. These networks can typically support mobility as connections are handed off from access point to access point as the mobile station moves.
Some municipalities are using WiFi mesh networks to support public safety applications (i.e. terminals in police cruisers) and to provide Internet access to the community (i.e. the city-wide hot spot).