I understand wharvey's concern about award becoming less frequent if coupons are to be bartered when it's not supposed to happen. When coupons come with restrictions, they are emitted by the hotel with the hope that they won't be used. It's the same with airlines miles. Many unfrequent flyers gather say 5,000 miles and will never be able to attain the minimum to claim an award. WIth hotel, the amount of the coupons is not sufficent to pay for a stay, so it will benefit you ONLY if you come back, and spend additional money. It's a lure and try to build loyalty. If the coupon can be sold :
* it can be used by anyone, so it WILL be used and a 100% use rate was perhaps not what was intended in the first place
* it will not buy your loyalty, because you might be staying elsewhere anyway.

So there may be a risk for the frequent guest program here : let's say an hotel can use $100,000 for a promotion. If they can expect a 60% usage rate, they will issue 2,000 coupons each worth $80. If they know the coupons will be sold on ebay, and that every guest will have one simply because he looked on the Internet, they will emit coupons worth 50. It will penalize the guests that used to benefit from the coupons because of their frequent guest habit, and I understand why they should be angry by the bartering of untransferrable awards.

Worse, the hotel could decide that since the award is benefiting anyone through e-bay, it's not worth the hassle to make a $100,000 promo and cuts the cost altogether.