Not the best idea imo...
The gravitational pull that makes the moon stay in orbit is Earth, if in case something does happen to Earth that would create a disturbance on the orbital path that it follows, if Earth would be destroyed entirely or any other possibilities that can alter the orbital path of planet Earth or for some reason the removal of the entire planet overall by some freakish reason, then what would be the point of having a lunar base, when the orbit of the moon is dependant on that of the Earth and the destruction of the Earth would cause a change in orbit to our Moon, who knows where the moon would actually end up, my best bet is that it would join the closest gravitational mass/pull available at the time, unless there are other forces that would therefore push the moon elsewhere, but it all depends on what the causes for the actual massive exodus are....unless the destruction created is localized (landmass area, planet remains intact as far as mass/size/orbit but no longer suitable to sustain life, etc) I can't see how the Lunar Ark can be used if the Earth is completly wiped off the solar system.
Sounds like a short term plan, but in the longrun, I would say looking after other planets would be much better than our closest satellite moon. Considering also other facts, for example, finding ice, water or bacteria on Mars, I think it would be the most suitable planet to start Terraforming...
Then again, maybe there was life in Mars before to begin with ;-).
Aside from all that, I'm sure that the people selected for such an Ark (if it were to take place) are the elite few involved in the military, government, higher 'ranks' or financial status. No place in the ark for middleclass working people ^^.
Cool articles Yiirk
, keep 'em coming!