MAC address filtering and WEP are the lowest common denominator for wireless security, you should not rely on either of them to protect your wireless network.
There are a range of security measures that you can implement if you want to keep your wireless net secure, depending on your needs.
Personally I run two wireless networks, one for my own in-house use and one for public access. Here are some of the security measures I have in place;
-Both are firewalled off from the rest of my LAN.
-Outbound raffic from the public WLAN is filtered.
-The Public LAN does not use WEP (though it did at one time use PPTP.) The Nocat http:/nocat.net authentication mechanism does dynamic firewalling and time-limited MAC address filtering (the time delay means there is a very short window when an attacker can hijack a MAC after an authenticated user's session has ended.)
-On my super-secure private wireless network, MAC address and IP address filtering are always in place for the specific devices allowed to connect. In addition, I use IPSEC (
www.freeswan.org) to provide a VPN connection.
There is a somewhat out of date diagram of how this looks (ignore the PPTP and WNAP stuff, that's no longer there) at
http://oob.freeshell.org/network.html
Hope this helps.
-Simon.