I must say that I agree that trading should be allowed, but also the NPC trading must stay too...
That way ppl can try to sell higher than the buy price of the NPC shop, while they can buy lower than those NPC shop item sell price.
For example : there's this M14 that's worth 9700 if you buy from the NPC shop, and then its sell price is at 5820. If there's an auction, some ppl that hate to be a sniper but found the M14 can sell it in the auction house for more than 5820, like say...9500, while the player who want to be a sniper can buy it from 9500, which is lower than those 9700 NPC price. Oh yeah, those item description while mouse hovering is also important, to make sure that everyone can see the base price of sell and buy in the NPC shop, that way they can't be scammed...
To think objectively, we must allowed the economy to grow even in Zombie infested city, and it's done thru auction-like market. Premium item must also can be sold in that Auction. That way ppl that can't have premium can also enjoy premium item, while the premium one can also gain money faster. That way, the dev can also have their only income (now, because they're jobless...

) and then can maintain good server condition.
For the real suggestion, visit this :
http://blog.zombiepandemic.com/Forum/tabid/65/aft/3445/Default.aspx Hopefully all you guys can agree to this and thus be implemented faster
