To date, Amazon has taken Google's Android operating system and used it for its own ends: creating an entirely separate app store, game ecosystem, and of course hardware ecosystem with the Kindle Fire. Today, Amazon is taking the next obvious step by offering developers a mobile ads API that will allow them to put Amazon-based ads in their apps in lieu of (or in addition to) ads from other networks — Google, for example. To participate, developers will need to include their apps in Amazon's Android app store, but the ads can appear on any app on any Android device, not just Kindle Fire devices. The ads will come both from Amazon and from "brand advertisers," which implies that the company is hoping to build a full-fledged mobile ad network — although for now the ads will only work in the US.
Amazon is promising "competitive CPMs" to app developers — the implication here and in a couple of testimonials being that Amazon's ads will outperform Google's offerings. Amazon even goes so far as to provide developers with a code sample that works first with Amazon's mobile ads then falls back to Google's AdMob ad network as a secondary option.
It's yet one more service that Amazon is offering to Android manufacturers and app developers to de-Google Android. Amazon has essentially built a second, non-Google ecosystem on top of the open source Android platform for its Kindle Fire devices, and with the new mobile ads API it is expanding that competition into new spaces.