This sure did work. I got one. A few people at my work did too. One actually went to two white castles and got a total of 60 for free. On one case he had pepper cheese on them and they only charged $5.48 for the case of cheese.
From what I am reading, it sounds like Corporate is becoming more aware of the "whoops". They are sending out an e-mail to all locations instructing them to only take the coupon from the people that are on a 30 page list of survey participants.
I would say try to get them while it lasts.