I fail to follow the reasoning behind that whole Hanson-Bishop
discussion that aliens would likely have a "kill them and eat them"
attitude rather than a "study them and trade with them" approach.
Perhaps the latest story to explore the scenario of Earth being invaded
by AI-driven nanites is Ian McDonald's 12/95 novel _Evolution's Shore_.
It starts with anomalies being observed in the outer solar system, soon
followed by probes which land on Earth and begin spreading a
cotton-candy-like nano-goo called 'Chaga', particularly in poorer parts
of the Earth like Africa. The story follows an intrepid reporter,
scientists and bureaucrats as they all try to find out what the Chaga is
up to and take advantage of it. In the end, all sides end up taking
advantage of each other (the Extropian approach?)
Mark Crosby