Ok, ok, you're too late. The free cases are no longer available, but the story is interesting.
According to the
New York Times, a merchant known as VIP Deals was selling their $59.99 cases for just $10, and if you gave them a review (they didn't say you had to give them a 5 star review) they would refund your $10. At one point they had almost 5,000 reviews and 4.9 stars on average. Unfortunately for them, Amazon wasn't amused and booted the merchant -- a search for "kindle fire cases by vip deals" now turns up nothing.
So, not big news, and the free case deal is gone, but an interesting story none the less.