The company I am working with at the moment is a cargo carrier with turboprop eqpm. They operate a variety of flights including cargo scheduled services in the UK.
We often get undeclared DG, some with road-only documentation or some without any. Any cargo found is put to one side and the CAA DG office informed. To my knowledge they have fined some of the shippers quite large sums of money. However it seems to have little effect as the shipments still keep coming.
The problem with DG shipments, especially via courier type customers is that the orginal shipper dosn't necessarily know that the shipment is going to be sent by air. To the average shipper whats dangerous about a sample of paint or some hair spray?
It's a very difficult problem to overcome and is basically down to the checking/acceptance staff at airports. However when shipments come in shrink wrapped and on a pallet it is difficult to check every box.