Correct me if I'm wrong, but in order to install apps from Amazon (or any provider that isn't the Android Market) you will have to allow third party apps, correct? Isn't this a security hole? I mean, it's not that I don't trust Amazon, but once your phone is set to allow third party apps, you can install ALL third party apps, from anyone. Now, I'm not stupid enough to download any old random app to my phone, but not everyone has such common sense. I can see the number of infected Android phones skyrocketing if Amazon or another competitor succeeds and actually takes a foothold in the Android app market.
I don't agree with Apple's walled-garden approach, being able to install third-party apps is nice, but for 50%+ of the population, it's an unnecessary security risk. A lot of people are really, really stupid when it comes to technology.