As others have said, contact them and see why it was denied. Pissing and moaning about it here isn't going to get you anywhere with them.

As for Rebates in general, manufactures and retailers love them because they know that 50-75% of the people will file them in to get reimbursed so it's extra money in their pocket. The Cabela's 12FV rebate in the form of a $100 gift card is twice as bad as first you have to file to get it and then you have to remember to use it before it expires. The percentage of gift cards that go unused is right up there with the number of rebates that never get claimed.