It's not at all difficult to become a Muslim. All you have to do is utter one line and mean it: أشهد أن لا إله إلاَّ الله و أشهد أن محمد رسول الله ("There is only one G-d and Mohammed is His Messenger"). Of course, if you are the child of a Muslim (as is Obama), you don't even have to do that. Born a Muslim, you are a Muslim for life. Under Sharia (Muslim law), if you renounce Islam you are an apostate (murtad) subject to death. Apparently, Obama's Muslim followers believe that he is still a Muslim. Otherwise they would be apostates themselves for associating with an apostate.
His supposed Muslim brothers (the non-biological ones) have set up a new website, "Muslims for Obama '08:"