The Amazon Appstore is pushing out a minor update this evening, brining it to version 1.14. Besides a few compatibility fixes and the ever-present "stability improvements," they have implemented a new system to help prevent accidental app buying. Now to purchase an application users will have to verify their choice, instead of the application purchase and download happening immediately after a mis-click. This should cut down the number of accidental purchases -- all those $0.99 apps really do add up. I've done this myself, so I welcome the change.
If you don't get the push notification about the update, you can manually initiate it by pressing the menu button, then opening the Amazon Appstore settings, where you're given the option to manually check. It's clicktastic!