Now Tom, be nice....this is one area where the code stumbles around some. Why, just a few months back, the IAEI ((inspectors' org) asked three experts, and came up with four answers!
The article was in the Nov/Dec2003 issue of IAEA news, was called "# Chiefs come full circle on parallel paths and end on a tangent," and you should be able to read it at IAEI.org.
For a very simple summary of MY view....
The ground rod is for lightning protection. Every building gets one.
The service is where the neutral and ground get separated...and stay separated. Every panel downstream get a ground wire sized to the current- and the ground rod at the other building gets bonded to this at the panel.
And...I don't care how balanced your loads are, or if there is only 240v. equipment in that other building....run a neutral to the panel. If in any doubt, it never hurts ti size it to the service the panel provides.
Two wires? Sure- if he only wants 120v.
