If you think really convulutedly then it [the prophecy] could have feasably been a Sith idea all along: 1) A Sith Lord (Palpatine? or possibly his master) creates the prophecy 2) The fufilment of this prophecy would be Anakin. 3) Using the 'Dark Lore of the Sith' mention in EIII, midichlorians are manipulated to create Anakin, the fufilment of the prophecy. 4) Palpatine becomes Naboo senator to watch over Anakin. 5) The Jedi are attracted to the plaent by the trade fleet in order to notice Anakin. 6) The Jedi train him whilst Palpatine manouvers behind the scenes. 7) The Sith trap is sprung, the Jedi are brought down from the inside by the Sith created prodigy. 8 ) The unforeseen part, Anakin throughs Palpy down the shaft after retaining a tiny spark of good. Thats the outline of what i've been thinking on anyway, I could write it in more detail later if thats a bit brief. Hows that for a hypothesis?