The "Obama is a Muslim" issue
I recently came across a more interesting version by Daniel Pipes. His argument is not that Obama is a Muslim but that, from the standpoint of Muslim law, he was a Muslim as a small child, at a point at which he had a Muslim step-father whom he occasionally accompanied to the Mosque. If so then, from the Muslim standpoint, Obama is now an apostate, a Muslim who converted to Christianity. Under Muslim law, it is permissable to be a Christian (or a Jew or a Sabean--along with Muslims the four "peoples of the book"), but for a Muslim to abandon Islam is a serious, indeed capital, offense. Hence, Pipes argues, Obama might have problems dealing with Muslim leaders.
So far as I can tell, the argument is at least plausible. I am not sure what the Sharia rules are on the age at which a religious choice counts, but I am pretty sure that repeating the formula "There is no God but God and Mohammed is his prophet" is supposed to make one a Muslim, legally speaking, and it seems likely enough that a child who attended services at a mosque would have repeated that formula at some point.