Don't let wireless security slide... With postage stamp size antennas you may only have a few hundred feet of range... With a large directional antenna you can get miles of range.
Also, many folks leave their routers setup with default passwords assuming nobody can get in... Yet, many leave the corporate name (like netgear or belkin) advertised on their wireless networks with no security. Somebody with virtually zero experience can hack that...
In the end, WEP is probably OK, WPA is better. Look at the value of your network/data to decide how much effort it is for somebody hack.
If you have 33kbaud dialup and your term papers on your PC--nobody is going to take the effort to hack. And, if they do, you are not out anything. If, you are running a high-tech startup and people are willing to spend hundreds of thousands of dollars to hack your system--nothing is safe.
And, remember that all of your data is going over the Internet anyway in the clear (unless you are using https or other security scheme).
In the end, professional hackers are going to go after large databases that have valuable information (like credit cards and corporate/government databases). The script kiddies are going go around your neighborhood and see what kind of grief they can cause.
The only reason that somebody will hack you is to get free Internet and your own data... Usually, this is only worth a few hundred dollars at most.
And, in the end, probably most of the home security break-ins are because somebody ran a program from a friend/web site, or opened an email that installed software to violate your security.
Most people are not running web servers and ftp servers that provide access points (assuming that you have file sharing turned off--if it is turned on, you are very vulnerable).
-Bill