well, i sent an e-mail to nintendo and i got not one, but TWO responses!
"Hello,
The only explanation of the problem you are having is that someone you didn't know visited your town and this person had hacked the Animal Crossing: City Folk game, which may have affected your game. Our recommendation is to share Friend Codes with people that you really know.
Sincerely,
Dervin Camden
Nintendo of America Inc."
and
"Hello,
The items you mentioned are created using a device that is not licensed, supported, or endorsed by Nintendo. Therefore, we do not have any information about how they will affect your Animal Crossing town or how they may affect visitors to your town, either via the Nintendo WFC or local wireless.
It is for this reason that we recommend you only exchange Friend Codes with people that you trust. This will minimize any chance your town will be exposed to towns or items that were used with unlicensed devices. At this time, we are not aware of any hacks that can cause damage to the game. However, if you are still concerned, you can delete the game and start a new one, and be careful about who you visit in the future. If your game appears to be functioning normally at the moment, this is not necessary.
For future reference, Nintendo of America Inc. is only able to provide product support for consumers in the Americas. Having said that, you can get any additional help you need via Nintendo Australia. I've provided a direct ]http://www.nintendo.com.au/nintendo/service/index.php[/url]
You may also call them at (03) 9730 9822 anytime Monday to Friday 9:00am to 5:00pm (EST) to speak to a Nintendo Australia representative.
Sincerely,
Alain Dao
Nintendo of America Inc."