Now obviously there will be alot of trading in SMP, but instead of having to drop your items and the other person pick them up, why not a separate menu. Now obviously it isnt the most needed thing to have, but its for a boost of organization and convenience.
The way it would work is you would walk up to someone- anyone, and if your cursor is on them, their avatar would have a black outline. From there you would right click and there is a list of separate options:
Inventory - Check the persons inventory
Trade - Trade with the person
PM(?) - Talk to the person, but nobody else can read it.
Well anyways, staying on topic, If you click Trade then two verticle windows will pop up. In the middle of the two windows will be a separate, smaller, window. You would than select what you want from the person, and what they want from you. The middle window would say "You are giving *name* your *item/ore/tool* For his *item/ore/tool* Accept?" If you dont accept than you would need to continue to bargain, but hopefully that wont be the case.
Now you could give as many things as you want, and wont be limited to trade one thing per trade, along with if you choose to give the guy nothing for your 5 coal, the computer would allow that also.
Now obviously its not needed, but its just handy in case a passing by standard accidentally picks it up. Im just saying it could be useful.