Terrorist Hoax Improvements Act of 2007 - Amends the federal criminal code to: (1) expand the prohibition against conveying false information and hoaxes to include false information and hoaxes about any federal crime of terrorism; (2) increase maximum prison terms for hoaxes involving a member of the Armed Forces during war; (3) revise civil liability provisions to allow emergency personnel to seek reimbursement of expenses from the perpetrator of a hoax who receives actual notice that such personnel are taking emergency or investigative actions in response to the hoax and who fails to inform one or more parties of the hoax; and (4) expand the prohibition against mailing threatening communications in the United States or to a foreign country to include threats against corporations and governmental entities (as well as individuals).