Archaeologists often claim that collecting is the driving force behind looting. I would instead suggest that looting is far more likely to be a byproduct of development. When roads or dams are built, unofficial "salvage archaeology' often takes place, which in fact may save some of the artifacts (if not their context) from destruction.
In China, this is certainly the case. According to a recent article, some 30,000 items on a 1982 list have vanished, in large part due to China's aggressive development. See http://www.guardian.co.uk/world/2009/dec/14/china-historic-sites-survey
Some experts think the problem is even greater than official surveys suggest. The article quotes He Shuzhong, of the Beijing Cultural Heritage Protection Center, as stating,
The last 20 years have been the worst time for cultural heritage site protection with the rapid development," he said. "It is even worse than in the Cultural Revolution – then, most damage was to movable items, but not to ancient tombs or buildings or old towns. For example, many ancient tombs have been robbed and in the [redevelopment] of old towns many old buildings have been demolished. Beijing used to have 25 protection areas and I believe only half of them are still well protected now.