Adam Engst discusses how to evaluate your rational risk when running a wireless network: My co-author on The Wireless Networking Starter Kit spells out a methodology by which you can determine whether or not you should have high concerns in securing and operating a wireless network.
Adam divides his evaluation into Likelihood, Liability, and Lost Opportunity: how likely is your network to be tapped into or cracked? how liable are you by having your wireless data exposed? and what are you putting yourself through by over-protecting a network?
It's easy to have a knee-jerk reaction to secure a network at the highest level when your actual needs are extremely low. While we rail against WEP (Wired Equivalent Privacy) all the time on this site, noting how weak it is as a first line of defense, for home users with few nearby neighbors and relatively little traffic WEP is perfectly reasonable.