Using current or just-over-the-horizon technology, would it be possible to construct moon base armed with a mass driver weapon? Would such a base be able to dominate the world by hurling lunar boulders at targets on the Earth? Where on the moon would the base have to be located? Are there any areas of the Earth that would be out of reach of such a weapon? What are the limitations and advantages of the lunar mass driver? Could it be the ultimate weapon of mass destruction?
I couldn’t get your link to work…but I think by the time anything like that was available on the moon we’d just simply shoot it dow with the newly designed 2000’s-style-positron-death-ray-particle-accelerator. 
Mass drivers on the Moon will be a vital part of the Lunar economy, if all goes well; power derived from sunlight could be used to export the aluminium, oxygen, silicon and titanium found on the Moon into orbit and around the developing solar system.
however Robert Heinlein pointed out that those same mass drivers could be used to drop rocks on the Earth; by the time the rock has fallen from the Moon’s gravity domain to the surface of the Earth, it will have a remarkable amount of kinetic energy, and thanks to libration no part of the Earth would be safe.
Heinlein didn’t really make a big deal of the chance that an IPBM (Interplanetary Ballistic Missile) could probably take out the mass driver quite easily, if the location was known;
but once the first mass drivers are built up there, you can expect that these missiles will be ready on Earth for just such such a circumstance.
A little picture of the Colonised Moon with an equatorial mass driver as a bonus.
Huh. Sounds a little like a railgun. I’ve heard of maglev variants of this.
Anyway, I’m not making this up (though I can’t vouch for the veracity of what I was told): I know a guy (I know, I know, sounds fishy already, but I swear I’m being honest here) who was working for a big weapons contractor. They were researching, he says, railguns designed to shoot tiny projectiles at massive speeds. In a vacuum, it’s theoretically (and perhaps practically) possible to get some projectiles up to speeds where relativistic effects are important, and the momentum of the thing is way beyond what you could currently attain trying to accelerate larger projectiles on more conventional designs. That’s all I can say on the subject, because that’s all he would tell me. It occurred to me this would only be useful as a weapon in space, because even railgun projectiles would maybe lose too much energy to friction, and possibly burn up. Or you could build one on the moon, I suppose. Why the military would be interested in such a thing is certainly intriguing.
So you’ve just been reading “The Moon is a Harsh Mistress”, eh?
The obvious problem with such an approach is that the launcher could be taken out with a nuke in no time flat. (Okay, a couple of days.) In fact, it would be destroyed before it was even operational if needed. In the Real World, enemies retaliate. End of speculation.