Message Passing & Distributed Entities

I find the combination of the next 2 patterns for software systems extremely elegant:
1) the Message Passing, and
2) the maintenance of Distributed Entities by the former.

They have been em employed in (at least) the following:

• Erlang Actors
• Mikrokernels
• Qnix
• JNI
• Java Spaces
• 3d virtual reality applications (FPS games)
• [edit 30-Sept-2009]Google-wave.

I think its the later that would become the killer-application of all times!