I agree with all your points, Tim. Distribution and memory models are trivial matters.

Sure there are risks, but APIs can be misused too. Pushing the clustering behaviour into configuration also doesn't sound like a bad idea to me - it's arguably more of a characteristic of the target environment than of the system type. It also follows a common theme from QCon, that of reducing the cost of change.

I certainly wouldn't advocate letting a development team run wild on it just because it looks like vanilla Java. Similarly, I wouldn't consider configuring java.util.concurrent.CyclicBarrier as clustered. However, I like the idea of being able to write my own abstraction for these essential items without having to learn (and hide) someone else's abstraction.