Hobbyists, also, frequently trade, buy and sell artifacts. All too often, important excavation data is not included with the transfer of the artifact and unfortunately another piece of the puzzle will be lost from the scientific record. The archaeological community (both the professionals and the amateurs) have tolerated this type of activity because these hobbyists occassionally share their site locations and a small percentage of this data gets recorded. However, in the long run, the hobbyists who do not record this data with the PASS files, are doing more harm than good.
Unfortunately, in recent years, it has become increasingly common for hobbyists to dig for artifacts. Scientific archaeological excavation focuses on the three dimensional mapping of artifacts and features within natural soil horizons. It is a complicated process. An archaeological excavation is a destructive process and it is necessary to collect as much data as possible to reconstruct the natural and cultural environment under which the artifacts were deposited. It can not be learned in a weekend or even in a summer. To understand and appreciate all of the intricacies of how to excavate a site requires years of training.