WPA is actually much more secure than WEP. MAC filtering is a good way to do it. War-drivers are a concern here in Portland, which is full to the brim with geeks. I don't know if OSB has these concerns. The overhead from using WEP or WPA isn't that much, maybe 1%. One concern is liability from an unauthorized user co-opting your connection for purposes such as spamming, file downloading, or child pornography. It's just better to have some security on. Now if you don't want to use encryption or MAC filtering, most AP's allow you to turn off their broadcast feature, which means the SID isn't broadcast. This makes it hard for a war-driver to connect since he needs the SID so he can associate to your AP. But he will likely know there is an AP nearby, and the proper tools can help him scavenge that SID.
