The final point at today's Google event was that Google is readying the ability to support in-app purchases. In a very great move for developers, the ability will allow them to charge for additional levels, consumables, and other after-purchase needs.
The ability has been in other mobile platforms for quite some time and really attracts developers as they can create a more constant stream of revenue. In-app purchases will be done through Google's servers just how purchases are handled now.
Google plans to implement this feature soon and applications such as Jelly Car and Tap Tap Revenge are ready to support it as they move to the Android platform. Tap Tap Revenge will be ready for release this spring when in-app billing is made available for the Android platform.
Developer information as well as the code for in-app billing is now available in the Android SDK, and in-app purchasing will be made available before the end of this first quarter.