This is just a soft science thing here, but also keep in mind that if your contact got pinched or otherwise gave up information about you, you'd have to make a choice. Do you want one contact that can tell authorities or enemies that you bought 6 pounds of C-12, a detonator, and a blow-up doll? Or would you rather that the authorities had to track down 3 contacts, verify that they're talking about the same person, and then link together the plot to blow up Dunkelzahn's car with a blow-up doll?