Right now, I think Iceland really needs more aluminium smelters, or similar, to help to recover their economy. I don't know what else they have apart from fishing and tourism, now that banking has collapsed.
But I wonder if anyone has ever properly investigated the consequences of over-using geothermal power? There must come a point when something bad happens.
On the other hand, all that steam circulating deep in the earth is busy depositing minerals. Maybe by using a suitable process, useful quantities of rare elements can be brought to the surface along with the steam. Gold, for instance. Now that would be a new form of mining, but I don't think that it would leave holes big enough for us to explore, somehow.