This idea fails a basic reality check -- piracy. During my around-the-world solo sail (http://arachnoid.com/sailbook) I heard any number of accounts of cargo vessels being boarded by pirates late at night, to steal cargo and slip away undetected by the skeleton crew that shipping operators prefer. The idea of a robot vessel would only make this problem worse.

The article says, "Unmanned ships would also reduce risks such as piracy, since there would be no hostages to capture ..."

But much piracy, for example in the eastern Indian Ocean, is after cargo, not hostages. Pirates could disable the propulsion system of, then loot, a robot cargo ship in the far reaches of the Indian Ocean where governmental controls are much weaker than elsewhere.