Several years ago I worked for a company that made a usb+network and usb-only skew of their product. The usb-only boards were the same as the usb+network boards with a few parts not populated.
We started getting tech support complaints when we sold the product into China. Turns out, an enterprising vendor bought a single usb+network printer, desoldered the EEPROM (containing the ethernet mac address). Then that vendor bought usb-only (cheaper) products, added the additional parts and bulk copied the single eeprom image (with the mac address) onto the new products, selling them as the more expensive usb+network sku. Result: a dozen+ of our product running on the LAN with the same mac address.
We started getting tech support complaints when we sold the product into China. Turns out, an enterprising vendor bought a single usb+network printer, desoldered the EEPROM (containing the ethernet mac address). Then that vendor bought usb-only (cheaper) products, added the additional parts and bulk copied the single eeprom image (with the mac address) onto the new products, selling them as the more expensive usb+network sku. Result: a dozen+ of our product running on the LAN with the same mac address.