Difficult subject this one and v emotive. I can understand why people go poking around on sites, from my perspective it would be the shear curiosity and excitement of finding something ancient and fuelling my passion for archaeology and ancient history. However, I would hand anything in that I found as you'd still get the excitement of discovering it but also it would be properly recorded and further proper investigation could take place if necessary. But I think the situation is totally out of control and it's sickening that there will be amazing and beautiful stuff out there which had been ripped out of the ground by night hawks which we will never know about. Imagine if stunning peices like the Battersea shield or helmet were found now, the chances are they'd be on the black market in a falsh if not found by archaeologists. These links to our past are so few and so precious that they need to be protected. People who purposely go out to find stuff to sell are scum and totally selfish. There is not an inexhaustable supply of this stuff. Once these things are gone that will be it.
PS this only goes for people who sell important historical artifacts, I don't have a problem with people digging up marbles and keeping them