Unlimited Friend Vouchers
To execute this cheat, you'll need 2 SD memory cards. Copy and save your game from your Wii to one card, and then go back to your game on one card and send out your Vouchers. After you receive your Vouchers in return, save your game to the other SD card (so that you have an old save and a current save). Whenever you want to send more Vouchers, just save your game to the current SD card, reload the old save game, and send out more. Then reload the current save to receive the Vouchers. In this way, you can easily get as many Friend Vouchers as you want.