"How such a retarded rapper managed to get AP attention to him?"
A retarded rapper?? Jay-Z might be a lot of things, but he is definitely NOT retarded. Also, the watch is really not all that blingy - in fact its hardly noticeable, the arabic '10' marker is replaced by ten small diamonds. Definitely not the most blingy of the royal oak line.
One of the most fashionable men in recorded history, the fabled Duke of Windsor, wore his watch over his sleeve. If you have the balls and are stylish enough to pull it off...why not? Its all about how you wear it. If you are dressed in Savile Row bespoke, and have confidence that borders on arrogance, then by all means wear it well.