There is a nice map with the article.
“Only 30 percent of the networks discovered in Mr. Lara’s survey had turned on the encryption system in their Wi-Fi programs, called WEP, to secure their data. And even that encryption is crackable with some effort. On unsecured networks, a passer-by or neighbor could record all traffic or gain uninvited access to local machines and an Internet connection. (Some of the private networks may use other security methods, like commercial firewall software or virtual private networks, that may protect data but leave the Internet connection open to freeloading.)”