I think this is a bit misleading.  If I do this:

    def foo = Action.async {
      WS.url("http://foo.com").map(response => Ok)
    }

This is a "quick, non-blocking operation", but is also an asynchronous action.  The intent of this page is to describe how to implement actions such as the one above, not how to implement actions that block.  I think we should keep this part of the docs talking about purely non blocking operations that involve futures, such as the one above.  Then we can have another section talking about blocking operations and CPU expensive operations, and how to delegate them to other threads using execution contexts or Akka if desired.