That also sounds a lot like DCOM and CORBA. Synchronous rather than async, I know, but making the network transparent is usually not a great idea; networks are so unlike method calls that reliability, performance, throughput, any metric you like will be far, far worse without extreme vigilance.
There is a difference between designing a system where objects always behave similar to network nodes and designing a cludge... I mean, a protocol that allows procedures to be called across a network.
I'm not saying that message-passing is magic and transparently solves all the problems associated with distributed computing, but conceptually it's different from RPC. In fact, it's kind of the opposite of RPC. Keep in mind that Smalltalk 72 was developed in the same environment (Xerox Park labs) that gave us Ethernet and developed large parts of the conceptual framework underpinning our modern networking.
