The network is not the computer
Patrick Logan: The network is not the computer. My computer is over here and yours is over there. All we need is a simple way to exchange documents. The documents are the messages. The computers are the cells. (Fortresses in Roger Session's metaphor.) The connections should be as simple as possible and get out of the way
This is definitely a vision I share. And one that I see embodied in the web services stack. Admittedly not in section 5 or soap:operation, but in headers and types.
The most underestimated problem that I see (and one that I harp on consistently here) is coping with the dimension of time: specifically how interfaces evolve.