Literally hundreds of sites a day disappear or are severely damaged from looting. The antiquities market is substantial. E-Bay artifacts example. Some looters are subsistence diggers as in the case of St. Lawrence Island discussed in the reader, where the digging and sale of antiquities comes from the people's own past and is used to support traditional life ways. Difficult to criticize this too much.
Legislation can help, but enforcement is difficult at best.
Progress, in the form of construction, landscape alteration, farming are the worst. But even CRM is difficult when the larger community doesn't want to cooperate. Farming may be among the worst activities for site destruction. To some degree, archaeologists themselves are a problem if they have an attitude that doesn't consider what the past means to these other groups. We have only recently understood our level of accountability to a wide range of publics.