We have to have Wi-Fi available everywhere -- I have withdrawal symptoms if I can’t do my email and check the web often. Recognizing this, many stores offer customers "free" Wi-Fi. I’m sure the cost of the Wi-Fi is passed onto the customers as higher product prices, in what are typically competitive retail industries. But how to avoid people spending hours in the shop surfing the web free of charge, and perhaps causing congestion for other users?
The Whole Foods store on Kensington High Street in London has solved this problem by allowing each computer or smart-phone a two-hour log on period, after which the device is booted off the Wi-Fi. Two hours are enough to satisfy almost any customer, but short enough to prevent non-customers from making the store their Wi-Fi venue of choice. I expect this kind of limit will become more widespread shortly -- it is much more effective than warning people not to stay logged on for very long.