obama held dual citizenship status until age 21.
Obamas own organization — the annanberg foundation byo factcheck.org admits he was a dual citizen until age 21
http://factcheck.org/2008/08/obamas-kenyan-citizenship/
the story above coincides with obamas change of citizenship status.
His natural citizenship was to Great Britain. His legal citizenship is most likely Indonesian after being adopted at age four. As president Obama has pushed Kenya to allow for dual citizenship. He has a vested interest in still being Kenyan on top of being Indonesian.