Art theft

Art theft is usually for the purpose of resale or for ransom (sometimes called artnapping). Stolen art is sometimes used by criminals as collateral to secure loans. Only a small percentage of stolen art is recovered—estimates range from 5 to 10%. This means that little is known about the scope and characteristics of art theft.
More information on the Wikipedia page - which includes a listing of some art thefts, and bodies involved in the recovery of such items. 
There is also much coverage on the internet.
See also Document theft
Category:reference