A few years ago I signed up for the FON service whereby in return for allowing free access to my internet connection to any FONeros who happen to be in my neighbourhood, I get access to a range of internet connections that have been shared out by other FONeros throughout the world.
I thought (and still do think) that this was a great idea. However, as far as I can tell my access point has only once been used by a visiting FONero (probably because I live in a quiet suburban area rather than a busy city centre location that would get a lot of traffic. In additoon I never actually used anyone else's internet connection when travelling. A few times I looked up FON access points in an area that I planned to visit, but in all cases I found it hard to find the FON access point that was indicated on the map and surprisingly enough I always found that there was somebody not associated with the FON service who was already sharing an open wifi signal.
As it happens, I had an Open wifi access point in my home even before I joined FON because I am not really concerned about the fact that any visitor might want to share my internet connection. I wondered how many other people share a similar attitude to me. To find out, I installed the Barbelo application on my mobile phone and ran a scan while I was walking the dog though the neighbourhood where I live.
What I found was that about 7% of wifi signals are not encrypted. Because I live in an area with a lot of houses, there were plenty of open wifi points available (as summarised on the following map).
View Open Wifi Points in a larger map
I am sure that some of these people left their wifi signal open by accident and did not intent to share access to their internet, but I am sure that several others are deliberately leaving their wifi signal unencrypted as a courtesy to strangers who might be in urgent need of access to the internet.