I know I will get flamed for this but it needs to be brought up and resolved.
Making all zen purchase account bound items would eliminate the backlog we see today for the zen exchange. Many players took advantage of the sale we just had and bought stacks of wards, both coal and pres. Than these said players will sell the item well above its actual value. Than because they have so much they are in no rush to convert the AD over zen. They will wait until the next sale and repeat this process. These players are the biggest culprits to the backlog.
Just using 1000 zen as an example if you bought the pres wards on sale from last week you could acquire 16 packs of pres wards. After the sale ends and a bit of time that player can sell a stack for 70-80K AD. Actual value given the current exchange is around 50K. At 70K for one of the packs the player is earning 63K AD. Using the 16 packs of pres wards that player would earn over 1M AD. Than simply using the zen exchange that player would end up with 2K zen. Rinse and repeat and over time that one player using this method can earn millions of AD without ever doing anything else in the game.
The game should not allow this behavior as these players are causing the backlog for the zen exchange. By making items acquired through the zen store bound this would remove quite a bit of the backlog we have today.
Making zen items account bound will not impact the game F2P model. It will help remove quite a bit of the zen backlog we have now.