*Good News:*
I was just informed that in three to five business days, a credit should be posted to my credit card. And that this is a one-time exception, as the iTunes Store Terms and Conditions state that all sales are final.
*POTENTIALLY better news, given that I have used up my one time exception:*
I was also told that "...the iTunes Store provides a warning message that asks if you are sure that you want to buy an item. This warning can be turned off. If you would like to make sure that this warning is on, you can reset the warnings in the iTunes Store by following the instructions in this article: Resetting iTunes Store warnings
http://support.apple.com/kb/HT1734"
I emailed back to confirm that after "Resetting iTunes Store warnings" once the Mac Apps Store will never revert to one-click buying (ie. it will always confirm after the BUY button is pressed), but I'm still waiting for the answer...