As liron said, one-click is optimizing the user flow, but allowing easy undo. It is good UI design: Optimize the common flow (buy the item) and provide easy u

As liron said, one-click is optimizing the user flow, but allowing easy undo. It is good UI design: Optimize the common flow (buy the item) and provide easy undo (from the post-purchase confirmation page, and in the delay before shipping). But I've still only used it a couple of times - the psychological barrier, wanting to include an add-on item, etc.