Microsoft's campaign against Xbox mod chips has ratcheted up a notch with the launch of the Xbox Live online gaming service. According to a posting at Got Mod?, (there's a site that's going to be pretty concerned about the issue) the company is attempting to detect mod chips when users connect, then placing them on a banned list - forever.
If this really is the case then it means we're already seeing how unique hardware IDs could be used in anger by certain companies. Because it's the unique ID of the Xbox that's claimed to go onto the banned list.
Read more: The Register.