I wish for a cake.
I wish that my first wish is fulfilled by a poster 5 post down.
Granted, a fruitcake is coming to whereever you are. You might say no, but you couldn't. You'll have to eat the cake or the cake will chase you forever.
Granted, but the poster suddenly disappeared mysteriously. There's no guarantee that the 4th poster down from here would do as you had wished.
I wish I wouldn't have to corrupt more than one wish anymore. That's too taxing, too cruel... :D