There's actually a Larry Niven story on this speculation. Its called The Hole Man, and is about how this group of scientists in an expedition to Mars finds this alien apparatus that uses a quantum black hole to communicate with gravity waves. A chain of events leads to this black hole being released from the apparatus and falling into Mars. The story was written just before Hawking came up with his theory so its probably possible to fault it on the Science now.
Anyway, for all we know there may be no Hawking Radiation after all(for it has never been experimentally verified)! What would this black hole do then. It would drill a neat hole to the centre of the Earth. Of course more than what it consumes, the greater damage would be because of tidal efects. This black hole would then oscillate about the centre of the Earth eating up matter and growing larger. It would be interesting to try and calculate how much time this would require but eventually it would eat up all of Earth and we would be left with a black hole about a centimeter acoss between Venus and Mars!
Of course it would continue to orbit harmlessly around the sun, but just imagine the immense possibilities that exist with such a black hole. Its possible to feed charge into a black hole, and then control it pretty easily. So if part of the human race survives, they would have a great technological tool at their disposal!