Depends. There are many ways to ban.
First way is his solution, IP Ban.
This only works if you have a dynamic IP. Most of you do.
Second way is to DNS Ban.
This way is counterable by using a proxy.
Third way is internet hardware ban.
It basically sends your MAC address of you LAN Port or 56k port. You can change your LAN port easily.
Fourth way is software ban.
This is a ban, that either when you wipe your computer or delete the file will you be able to play the game.
Fifth way is harddrive ban.
Basically this is a ban that bans your drive's volume number. This is counterable by changing your hard drive's volume ID, or running off a flash or USB stick or off your Ipod or PSP.