Obama is a star. Certainly the most popular celebrity in the world at the moment. When Obama met with Indian Prime Minister Manmohan Singh this afternoon Singh asked Obama for an autograph. His daughter is a big fan of Obama.
Autograph collectors have been aware for awhile that Obama's autograph is the most desired of any living person. Things can change in a hurry though. After George W. Bush's speech just after the 9-11 attacks, his autograph attained a valuable unmatched by any previous sitting president.
A January 2009 Autograph Collector "Commemorative Inauguration Edition" article valued an autographed 8 x 10 of Obama at $800 - $1500. One signed as president was valued at "up to $3,000."
A value of "up to $9,500" was estimated for signed true first editions of The Audacity of Hope. Latter editions were valued at the time at "up to $1,000."
Time will tell if those values hold. He is certainly facing challenges that will test his popularity, especially in the U.S. where he will be judged by the state of the economy after the "honeymoon" is over.