The Missouri Department of Health & Senior Services announced that beginning March 1, 2011 there are changes to the procedures for requesting death certificates. See their updated requirements here. You will now need to include a photo id when you request a death certificate and if applying by mail, your request must be notarized. The appropriate fee is also required.
This is a minor hurdle in my mind, I've been including a copy of my driver's license when requesting death certificates from New Jersey for years. Most generally, banks will perform notarization duties for customers with a small fee.
What I want to point out is that this new requirement applies to death certificates newer than 50 years. In Missouri, once a death certificate group reaches 50 years old the certificates are transferred to the Missouri State Archives. The Archives then scans the certificates and places them online...for free! Don't be confused by the announcement and think that this wonderful service (thank you Secretary of State Robin Carnahan!) is no longer available.