Certification of live birth

On April 21, the New York Times published an article about the state House of Arizona passing a bill which would require President Obama to show his birth certificate if he intends to seek re-election. The journalist wrote that "A scanned image of his birth certificate released in 2008 says he was..."
http://www.nytimes.com/2010/04/22/us/politics/22brfs-OBAMASBIRTHP_BRF.html

On May 13, the New York Times published an article in which the following was stated.
"So when questions about Mr. Obama’s birth first surfaced during the 2008 presidential election, his campaign posted a copy of his “certification of live birth” on a Web site.
http://www.nytimes.com/2010/05/14/us/politics/14hawaii.html?hpw

A question was posed on wiki.answers.com about whether a certification of live birth is the same as a birth certificate in Hawaii.

"The Department of Hawaiian Home Lands accepts both Certificates of Live Birth (original birth certificate) and Certifications of Live Birth because they are official government records documenting an individual's birth. The Certificate of Live Birth generally has more information which is useful for genealogical purposes as compared to the Certification of Live Birth which is a computer-generated printout that provides specific details of a person's birth. Although original birth certificates (Certificates of Live Birth) are preferred for their greater detail, the State Department of Health (DOH) no longer issues Certificates of Live Birth."
http://wiki.answers.com/Q/Is_a_certification_of_live_birth_the_same_thing_as_a_birth_certificate_in_Hawaii

Although I don't believe that President Obama was born outside the United States, I am curious why he hasn't produced his original birth certificate, thus providing greater details about the man who was elected to the presidency.