The manufacturer could then match their serial ID of the MAC address and match it to a company, and then customer, it was sold to.
How is this possible? When you purchase a nic card you dont register it with the company. The only way i can think that they can trace it back to you is when you install it and it asks you to register it. Even then i'm not sure if it sends the mac address in, because you dont always have to register online, you can send in a post card.

Please correct me if i'm wrong.

Keith