Here's how this works. You grant the wish of the poster anobe you, but you give it an unexpected and unfortunate/amusing/embarrassing/ironic twist. e.g. -- If the first person wrote, "I wish I had a million dollars", the next person might write, "Wish granted. You'd better pray the Colombian drug cartel doesn't figure out who took their money."
Then you post your own wish.
I wish I had more room for carnivorous plants!