I’m stopped here in Keene, NH for lunch at the Panera Bread outlet. They have free wifi, and a very friendly start page:

At Panera Bread, our WiFi is free and we welcome you to stay as long as you like. All we ask is that you give consideration to other patrons, particularly at busy times of day.

At lunchtime, for example, please try to use the smallest table available so that we can accommodate larger parties. Or, come back when things have slowed down and you can spread out your work.

Thank you for your patronage and consideration. With your help, we can all enjoy our sandwiches, salads, freshly baked bread and hot coffee — and free WiFi, too.

The is not only considerably more friendly than a “please limit wifi use to 10 minutes” rule, but also, I suspect, engenders a fierce loyalty to the brand. It’s smart friendly, in other words.