Strangeness of Design

I read an article today about how the facebook game farmville was designed with the help of psychologist who studied the aspects of human nature that compelled a person to complete a task. They then implemented these specific conditions into the game and its gameplay mechanics. The debate in my brain is whether or not this kind of design a manipulation of the audience or brilliant game design. By placing those psychological compulsion triggers in games it almost seems like there is no faith in the product to succeed on its own without relying on those factors within the game. However, maybe the key to making a really fun and hooking game is to use those factors subtly and to implement them sporadically amidst other gameplay elements. Games have addictive elements in them no matter what genre they are apart of. Games like World of Warcraft have that repetitive grinding to gain levels, shooters can just be assumed, etc.. I can't seem to fall down on either side of the argument though. I think that a designer should use a variety of elements in a game to make it entertaining and enthralling to the player but at the same time those psychological factors are part of what can capture a player's interest in the game. In my opinion its hard to say where one ends and the other begins with real games. On a side note the psychological aspect of all this is pretty fascinating.