This is more of a rant, but this is really bugging me.
Last Tuesday, I ordered a Furby from Wal-mart.com. A little while later, I though I found a better price else where, so I canceled the order (time elapsed about 5 min.). Wal-mart did warn that if the item was packed for shipping, they might not be able to cancel it. I later wished I hadn't canceled the order because the better price I thought I saw was exactly the same. Now, since I wasn't sure if the order had canceled, I waited a few days. Since I didn't see any change in the order status, I figured the order was canceling. Then I ordered it from Toys R Us.com. Then I got a warning from Wal-mart saying my item's shipment was delayed because it was out of stock and I could cancel if I wanted. Then on Sunday it shipped.
This drove me up the wall. Now I have two Furbies coming. What bothered me was that I canceled a few minutes after the order; they didn't have furbies in stock for at least two days, so it isn't like they had it packaged. They were just too lazy to cancel it. At least with Wal-mart I can return it to the store. (Which is what they so helpfully said in the email. Oh well, I go to Wal-mart a lot so no big deal.)
Amazon.com did the same thing to me last year. I pre-ordered a book I wanted. On the day it was supposed to be released, Amazon.com had it out of stock and they wouldn't let me cancel. It isn't like Amazon had it in a box ready to go, they didn't have any at all. It took them a week to ship it. I think when an item is out of stock, you should let your customers cancel the order.
I suppose from the retailers' point of view it makes good business sense. If they won't let me cancel then they will get my money. They are probably banking that I'll just wait for it and keep the item rather than return it. And they are probably right (except for the Furby, nobody needs two furbies). But they reduce future sales. I now know that Wal-mart's cancel button is just for show. And I will never pre-order a book on Amazon again unless it is something like Harry Potter where they swear up and down you will get it on the release day.