Sometimes you don't get what you think is promised. One of the most common providers of wi-fi service in local coffee houses is a company called ZRNet. They apparently got in the broadband business early and seem to have signed up a lot of local places.
The ZRNet logo is probably familiar to most local internet junkies.
But if you also see this in the window, don't be so confident that you can get online without paying for broadband access. You may buy your coffee as I did the other day, set up your laptop, and then find something like this on your screen:
ZRNet wants us to scared that public networks may be insecure. Or course they are. Most networks, even ones with passwords, are insecure if someone really wants in. But using a little caution, there's no reason to pay ZRNet to use their open network in a cafe. The "Surf Free" option is fine, if you can hold off on using your credit card or other sensitive transactions. Mostly, they are just trying to con the gullible and anxious into selecting "Surf Secure" and paying an unnecessary fee.
However some cafes are compounding the insult. They've apparently turned off the "Surf Free" option on ZRNet. If so, you get this screen:
I ran into this one at Royal Grounds at 3101 Geary Boulevard. They can forget my coming back there. I should have known when I looked in the window and there was no one else in the coffee shop at midday.
Hint: you can always go to the nearest branch of the SF Public Library if you need a connection.