Need to subpoena Facebook or Gmail? If you do, then you’ll need to know where to serve the subpoena. For example, how would you know that Facebook has an email just for subpoenas (firstname.lastname@example.org)? Do you know the office in Palo Alto and telephone and fax number for the Facebook department that accepts service?
You’ve gotta check out this site. It is meant for law enforcement but open to the public.