In his Wired article “Steal This Wi-Fi” Bruce Schneier gives some good reasons to leave your wireless network open, being neighborly for starters. While being neighborly is nice, advising people to open their wireless network without providing some advice on how to do it securely is irresponsible and one would have expected more from a renowned security expert…
My blanket advice – close your wireless network. If you don’t know how, find someone who can help you.
On the other hand – if you know how to run an open wireless network securely then do it! It may be a geek thing, but I find it cool (and neighborly) to be able to run an open wireless network and provide passersby with free internet access.
Here is how I do it: