Bill Clinton's complex web of international financial interests and reputation for outspoken commentary on US affairs could hinder Hillary Clinton's role as Secretary of State in the Obama administration.
You can certainly bet that if she were appointed to this postion, the media would be frequently interviewing Bill to hear his take on international affairs, in effect placing him as an eternal presence looking over Barack Obama's shoulder and offering critiques on the fly. Does he need that kind of second guessing in his administration? Who would want it?