I am very grateful to people who left open unsecured, WiFi access for me during my trip to Europe. With the small amount of bandwidth offered me, I was able to upload a photo to Flickr, check email, and add an entry here each day.
Carrying around a notebook computer is useful as long as access to the Internet is possible. With the spotty coverage of 'pay for' options, public access to personal broadband was a Godsend. This situation has forced me reconsider how I've set up my wireless router. I may go ahead and make it public. There are system logs, so if I find a neighbour abusing my generosity, I can add WEP again.
I might suggest that if you live near a park, budget hotel, or public area, sharing a little of your fixed cost Internet might make visitors to your area very happy!