In a thread on a metal detecting forum near you, complaints are being made about commercial rally organizers who take money from artefact hunters who then find when they get there that they cannot fill their pockets with bits of the site's ancient heritage due to the condition of the field (Another Rally with fields that are close to not detectable!!). In some cases, the ground is too rough (heavily ploughed, tall vegetation or stubble), or is contaminated by too much modern metal, or has been "done over" by other detectorists (so-called "responsible detectorists" do not seem to relate that fact to their own destructively erosive activity, of course...). In an example of the latter situation member "muddy fingers" (Sun Mar 06, 2016 9:15 am) writes:
I went on a small commercial rally last week where the fields were totally devoid of signals, apart from that given by silver paper. Hardly anything was found and a few of the detectorists were quite angry, especially as it transpired the fields had previously been visited and abandoned by another club. Fortunately for the organiser, one of his associates conveniently found a very nice large hammered coin. This is not the first time I've noticed this happening on some of these commercial rallies, though often it's a stater that is fanfared to justify the choice of site.That's a manner of use of ancient artefacts by collectors we've not seen discussed in the textbooks. If this is happening a lot (and we've heard others say the same thing), then the finds records from some commercial rallies must be considerably skewed. In what way are such items 'vetted' by the PAS, either on site or to whom these finds may be taken later in order that false "data" do not get entered onto the "database"? That is, by the way a serious question to the PAS, not the rhetorical one they will pretend it to be and ignore. Tell us how reliable we can expect your data to be if finds and reports are not vetted.
UPDATE 12th March 2016
Well, what a surprise... not a peep from the PAS, a tacit admission perhaps (because I can see you and your 'partners' are reading this) that there are few or no controls leading to a high probability that through inadequate vetting, the PAS "dataset" is potentially corrupted to a totally unknowable extent.
Vignette: "Hammered? Look what I found"