I just called two JoAnn stores in my area (Apple Valley, MN and Edina, MN) and I was told that their deal was:
Buy one yard of regular or sale priced fabric and then one could get one yard of selected clearance fabric for $0.01 a yard.
The limit was ten yards of regular or sale priced fabric and get ten yards of selected clearance fabrics for $0.01 a yard.
You might want to call your local store before making the trip.