This article talks about the insecurities of 802.11b and how to secure it. I found this article to be interesting. They even, went out and did a "survey" to see how many networks they could test, and how many networks where open. Read MoreQuote:

Armed with an Orinoco gold card, a 14 dB yagi antenna, and a 3dB magnetic mount omnidirectional antenna, we decided to run a "survey" to see how many networks we could detect, and of those networks, how many were open. These antennas, by the way, are not expensive. You can buy the yagi antenna for $126 and the omnidirectional antenna for $60. And if you really are interested in a high performance antenna, you can buy a 24dB parabolic grid antenna for $112.50