Certainly, I'm not a domain attorney. However, as someone who runs a domain name protection company, my advice is to one of two things: - Log into your domain registrar and delete the domain in your account. That will make it available for registration again, giving FB a chance to register it. - Respond to them and work with them to transfer the domain to them. This is clearly, undoubtedly a trademark domain. Any UDR…
Why would this be an infringement if no one would get confused between this site and facebook itself?
Actually, I just looked into this a bit. It seems like they just do this to anyone who owns a domain that has "facebook" in it. Don't think that they're actually that serious - probably a bot.