I was purchasing a system online last year, and was interrupted during the process of choosing my option. I had to stop and leave the PC for about 30 minutes. When I came back and finished my options, the original "deal" I had clicked on was no longer available! I called Dell and got the same "marketing error" excuse, and canceled the order.

About an hour later I went back to the Dell website and, what do you know, the original offer was right back on their homepage! I went in, again, clicking on the link for that offer, chose my options, and once I got to the checkout, the offer was gone!

Needless to say, i didn't complete that transaction, either.