This is almost definitely coming from eBay. It's important to recognize that this is a Cease and Desist and not an actual legal action. It's a threat of a leg

This is almost definitely coming from eBay. It's important to recognize that this is a Cease and Desist and not an actual legal action. It's a threat of a legal action. You really have two options -- either you give up the domain name or you fight. If you choose to give up the domain name, respond that you're doing so and I'm sure you'll get a brief letter thanking you for your cooperation on the matter. If you choose to fight, and that includes ignoring, responding with questions or telling them that you think they're wrong, don't expect to get any further response until they actually file to forcibly take the name from you. If this happens, you will have to pay money to defend yourself (no lawyer except maybe the EFF?) will take this pro bono or on contingency. You could also wait until they file legal proceedings to cooperate, which would enable you to keep the domain name for a while longer and force them to spend some money, but you'll still lose the domain in that case. For now, I'd personally ignore it. Either they're serious or their not. There's no reason to do anything until they show whether they're committed to getting this domain from you.