Amazon as a platform provider will be dangerous.
-Instant Prime account to access online, which means free 2 day shipping off all retail games (assuming it isn't 100% digital), access to Prime Instant at no extra charge, free ebooks, and everything else that comes with being a Prime member
-Kindle integration for whatever they want to use it for.
-Popular sales platform in Amazon.com with built in digital books, games, apps, music, tv shows & movie store
Which means sales and/or free books, apps, games, music, shows and movies. That's a HUGE day 1 library for browsing.
-cloud service already up and running
-massive servers capable of handling just about whatever needs they have for gaming
-infrastructure, customer service, name/brand recognition & deep pockets
-And soon, exclusive gaming content to go with their exclusive tv shows
That's allot of things going for it right out the gate.
Nintendo should be a little worried, setting as how Amazon already doesn't favor certain Nintendo hardware being sold on their site. MS & Sony should also be weary of what Amazon is doing.