Alaska has been in the news a lot lately, thanks mainly to the exploits of Sarah Palin and Ted Stevens. While I'm happy to let them drift away from memory, one news show comment that has stuck with me is that Juneau, the capital city of Alaska, is inaccessible by road. And it's certainly not alone. Many cities and towns in Alaska have no roads that go to them or have seasonal ice roads. So much of the United States has boundaries and roads demarcated by the rigid Jeffersonian grid (explored so nicely in James Corner's "Taking Measure Across the American Landscape") that you can feel confined in it. Environmentalists who opt to live "off the grid" could in many ways be referring to the Jeffersonian grid instead of the utility grid.
I think the rise of Google Earth and Google Maps has had a similar impact on our sense of the known, except on a world scale this time instead of a country scale. Sure the images aren't always the highest resolution, and they can be years old, but they do make the whole surface world feel very knowable. There is no uncharted Africa of Joseph Conrad's "Heart of Darkness".
So where do people go to really escape to the unknown? They need to shift vertically to underneath the aerials and the roads. The oceans remain largely un-surveyed. There are still caves to be discovered, and underground urban infrastructure to be reclaimed. Eventually, though "off-the-planet" may become the new "off-the-grid".