Just thinking, what would happen if BLTC keys were removed from storyline mission rewards and were made free items. They could be traded, sold on the trading post, etc.
They would become a currency, and people who want to gamble to open chests to get the rare permanent versions of the trading post etc would just buy the keys for x silvers off the AH.
This would probably drive up gem cost and also increase profits from the gem store as obviously the TP is player driven the key prices would fluctuate alot, but there is another option open to players who want the keys.
v0v Keys are good currency in TF2/Dota2