Just so you know, WEP has recently become very easy to hack. Previously brute force was required to break it, more recently there are tools which can pick out the WEP code from the signal however. A recent demonstration with tools commonly availible on the internet took 3mins to break 128bit WEP with a completely secure key.
http://www.tomsnetworking.com/Sections-article111.php
WPA however still requires over an hour and quite a lot of data (more than normal data transmission), however it is possible to completely freeze a WPA connection such that nobody can use it. This requires a simple signal to be sent to the access point and that makes the wireless part of it reboot.
Hiding the SSID does not increase wireless security at all to be completely honest.
MAC address control can increase security quite a bit if combines with WPA (perhaps WEP) but on its own it does very little as it is so easy to close a MAC address.
Ultimately any wireless encryption is crackable as overkill said. However, if at all possible always use WPA as it is now SOOO easy to break WEP. I could even do it in 10mins on my tiny PDA with its processing power!