Google blocked it. From this link:
The Android artifacts have been built
and published to the Maven repository
through the efforts of the Android for
Maven project. Google prevented the
official Android jars from being
uploaded to Maven, so the, third
party, Android for Maven project was
started to provide an API compatible
Android artifact that could be
uploaded to the Maven repository.
There are now artifacts for each major
Android version available in the Maven
repository. These are not functional,
however, and only provide stubbed
implementations of the API. All
methods in all classes throw a runtime
exception. Because an Android app runs
on a device, it will never use these
libraries for execution, but the API
compatibility allows an app to be
compiled as if it were the real
library.