Perhaps the definition is that to be a fence you have had to buy the good and take ownership (and responsibility) for the goods yourself. You then resell them

Perhaps the definition is that to be a fence you have had to buy the good and take ownership (and responsibility) for the goods yourself. You then resell them to pass on ownership. Otherwise you're just providing services, whether that's storage, transport or whatever. So do Amazon take ownership, or do they just sell them on your behalf?