Iron Mal said:The worlds greatest thief would probably be a man who no-one has ever heard of or seen, hence the fact that he's a great thief (it kinda defeats the point of being the planet's greatest sneaky bastard if everyone knows who you are and what you look like).
That makes sense, really. If you indeed would be the greatest, we would know of the heists he commited, but not who he actually is, so he's gotta be awesome =D!