Apple should ship orders in the order that they are received and not give preference to their own internally-generated orders. To do otherwise reduces MacMall and all of the other resellers to the level of second class or third class merchants. I would imagine that this situation is not pleasing to MacMall nor to any of the other authorized Apple resellers. It is certainly not pleasing to me, as it looks like it is going to take right at six weeks to receive my order.
Third party dealers save money by agreeing contracted quotas and ordering in bulk. Once they have filled their monthly quota of x-number of orders to secure their sales deals from Apple, they won't waste further orders from that month on an already-fulfilled quota – they'll wait and put them towards the next month's quota. And when that's filled, those left over will go on the next month's etc etc. If you've been waiting months for your iMac, it's probably because of your third party dealer having sales deals operating that underestimated demand.
I ordered my i7 2T direct from Apple on the 8th Dec and received it today (16th). There is no hold up at Apple. If people order through a third party, they put themselves at the mercy of that company's buying power (or lack of it).
If company x gets a contracted advantageous price for ordering (say) 200 iMacs a month, they won't order 300 this month. They'll hold the extra 100 to put towards the next month. If yours is one of those held back, that's the dealer's fault, not Apple's.