DanSC DanSC:
I think the reason the Louve doesn't use the same security as the U.S. Constitution is probably cost. The Constitution, Declaration of Independence, and Bill of Rights are kept in argon gas behind blast-proof glass. At night and at times of emergency, like 9/11, they are automatically lowered into a massive vault several, perhaps even a dozen, stories under the National Archives building in Washington.
Though considering the value of the Mona Lisa, such a vault is probably not a bad idea.
Well a vault MIGHT be a bit overkill, I think, but just having some case to enclose it doesn't seem too expensive, considering the immense historical and monetary value of the artwork. Hopefully they'll be able to properly restore the work to it's original condition