This is pretty annoying. I am not a drinker, but I hold onto the coupons for flights to Vegas with friends. And, then I give them a book of them to each friend. It has always been a nice way to start the weekend off right.
I fly WN probably 3 - 4 times a year for flights sub-500 miles from LAX particularly when there is a double credits bonus offer on. Usually there is a family trip mixed in their as well. In the past I liked being able to transfer credits from AMEX to WN to top off the accounts of family members. Now that option is done. I don't like to have credits/miles just waste away in accounts. So this has pushed me further from WN. If I am going to have wasted flights no miles earned, I would rather fly VX.
For me WN is slowly chipping away at its value proposition. This is an individual statement. I just feel that these types of policies slowly chip away at the value and that value usually stays gone and doesn't come back.