American Express and Twitter let you pay with #AmexSync

American Express recently announced that consumers who use Twitter will be able to pay for items using a special hashtag for certain products and websites.  After tweeting them what you want, you get a confirmation hashtag.  You then need to tweet back the confirmation hashtag, an email will be sent to you, then you need to confirm again that you want the product. It then gets shipped to your billing address.
Although this seems easy enough, a lot of questions come to mind.

The Gadgeteer , American Express and Twitter let you pay with #AmexSync, American Express and Twitter let you pay with #AmexSync