Amazon dominates the e-book market right now, and they have their Kindle app on all popular platforms, including Android and iOS. One of its bigger competitors is Apple's iBooks which now comes pre-loaded on iOS devices, so Amazon was a bit disadvantaged here, because it didn't come pre-loaded either iOS devices or Android ones.
But that's changing now. Through a partnership with Verizon, the Kindle app will come on some popular Android phones like Samsung Fascinate and the Droid series.This is a big win for Amazon, although it would be much better if Google would allow them to come pre-installed to all Android phones. But Google had their own book thing in mind with Google Editions, which we haven't heard anything about for several months. If it's still coming, it better be very competitive with the Kindle Store.
But now that Amazon has won this deal, I think we all know what's the next step. That's right - the Amazon App Store for Android. They've probably already sealed the deal regarding that as well, and maybe the Amazon App Store won't come on all Android phones, but it will definitely come to some.
But that's ok, because the Android Market needs some strong competition to get more improvements. In the end it wouldn't be so bad if we could have access to the apps on both markets, would it?