You brought up a good point there Sporge with the "special event" items. I think that maybe, if say they give out something like a Santa Clause hat for about two weeks around Christmas, and theres no way you can make it, "hacking" a few and giving them to a few friends and maybe selling two or three online is OK.
But, when people go overboard and sell out thousands of an item that was supposed to be extremely rare and valuable, that bothers me. I'll admit, I used my AR for Gamecube quiet a few times, but it was mostly for minor things or things that I couldn't have done otherwise, such as hacking myself onto AC Island. It's definetly something that needs balanced, but it's a very delicate balance.
I think maybe, to keep it safe and hack-free, they could create an "Antique Shop" in the city. About a month or so after the release of a "special event item", the shop could randomly pick it up, but have a limited stock of maybe five or so of each item, and a relatively high (but not unreasonably) price tag. Also, just as a fun way to interact with friends, some shops could only get some items while other shops get others.
Example:
For Thanksgiving this year, they release a six peice furniture set, including a bed, table, couch, chair, closet, and TV. For Christmas, they give out a Santa Clause Hat. Also, in between to celebrate the lead developer's birthday, they gave out a cool Nintendo shirt. That leaves us with 8 "special event items" that will appear in the Antique Shop by Christmas.
Now, Bob and Joe are friends. They both have City Folks. In Bob's store, the Thanksgiving bed, table, closet, and chair, and the Nintendo Shirt go up for sale. In Joe's store, they stock the Thanksgiving chair, TV, couch, and bed, and the Santa Cluase hat.
That's just an idea I came up with while reading this thread. I kinda made parts up as I went along. This system will help to deter hackers without making items impossible to get, and encourage interaction with other players.