Jacquilynne Schlesier has written a thought-provoking article about a Canadian copyright case (Maltz v. Witterick), where a writer used facts from a documentary to write a fiction book.  The lawsuit took place in Canada, so the ruling - in favor of the defendant (J.L. Witterick) - might turn out differently in another country. Still it is interesting to note that basing your work on someone else's may not be illegal.