If the CIA theory pans out, it wouldn't be they turned on him, it would they found him out.
Use your head. The CIA isn't going to send a Jewish kid into an Islamic lion's den with his real (Jewish) name and real passport...a passport that had his visit to Israel stamped in it.
You've already seen his dad on TV and seen his college friends, so you *know* that Nick Berg was the real name of the kid. People knew this kid. He has a history. Made up names for Black Ops run by the CIA don't have that level of made up history where everyone at the kid's college would be able to blow the cover out of the water.
So the kid ain't CIA.