Unlike Maven 2, Maven 3 supports out of the box only http:, https: and file: as transport protocols. To use other transport protocols like scp:, the appropriate wagons have to be explicitly declared in the POM as a build extension. If the wagon in question is only used for deployment to a repository, it can alternatively be declared as a dependency of the Maven Deploy Plugin.
Therefore, for us to release using Maven3 we need to use the extension.
This has also become an issue for us in Maven 2 when using OS X 10.7. There was a repeated prompt for the password event though we are using ssh keys, the maven settings were correct, and ssh to the box works without password.
The required mods are simply:
1. Change all deployment urls to be the scpexe protocol (i.e. every url in distribution management, including the site url)
2. Add this to the <build> block:
<!-- Enabling the use of external ssh -->