Well, this is quite the development and is sure to set a fire under the rug for most people. The only method that Kindle Fire owners will be able to install apps is through the Amazon Appstore for Android, it does not ship with Google's Android Market, period.
This means that Android developers need to make sure that their apps will be available on the Amazon Appstore, if they want to get a piece of those 12 million Fire owners that Amazon hope to have in 2012. Right up until now, Amazon has been very Apple-esque in the way that they treat developers, and publishers. By having your app on the Amazon Appstore, you give up more control than Apple actually asks of you, with you giving up the control to set your own price and control your app's description, with more restrictions behind those Fire-y curtins.
Google's open approach to the Android Market is what draws a lot of people to it, versus the rose-tinted world of Apple's App Store, or Amazon's Appstore. If the Fire does indeed sell 12 million tablets next year, what will happen to owners who want a game, or app that just isn't made available on the Amazon Appstore? I hate to think that Amazon could have this plan back fire on them...