tault_supervious wrote:Only works with items that are tradeable?
No -- You don't actually trade any items.
When your partner opens a trade window with you, it locks your inventory. That way when you turn in the quest, the quest giver can't take the quest items away from you. As long as you pick the quest back up again before "completing" the trade to close out that window, the quest items will remain in your inventory.
*Edit*
One of the ways they are using to catch people is the fact that the vgplayers database tracks the number of quests you complete. They can look at people that have a very large number of quests completed within a very small period. So just be careful.