It used to be that NPC vendors would only show a certain amount of player sold items in their inventory (may still be that way). If you completely bought out a player sold item, that slot would fill up with one of the "hidden" items that was sold to the merchant. The next time someone sold an item that was just bought out, it would drop into the "hidden" inventory, if the merchant had a lot of stuff sold to it. Buying out the last blue diamond on a well used merchant (like the ones in the guild lobby) means that the next person to sell a blue diamond to that merchant will basically be sending the BD to the void since it won't show up on the visible inventory. This means that people buying up blue diamonds to skill up on jewelcrafting will most likely not be able to buy blue diamonds off of that merchant until the server is reset and space is available again. Like I said, that's how it used to be. I'm thinking it's still that way.
