Whether it's Zynga's astronomical "market value" or FourSquare's skyrocketing audience, one can't help but wonder whether these are truly strong platforms, or sparks of inspiration that will flame out in the absence sufficient utility to sustain user engagement.

Social game dynamics have two things going for them: the traditional hook and addiction of game dynamics, and the drive, amplification and distribution of social dynamics.  Together, they are a powerful force.

Social game dynamics will draw in a user and hook them.  Game dynamics will capitalize on basic human drives to foster addiction to the experience.  They foster the desire to push a little bit harder to achieve that reward that seems just beyond your reach.  And once you achieve that reward, you see the next, and it looks enticing, because that reward is just a little bit further than the last one.  Social dynamics make these singular actions into a community of addiction and drive.

To be fair, I am a self-labeled Zynga addict.  I checked out Farmville way back when it started to gain momentum (almost a year ago), and somehow ended up addicted and heavily engaged.  I was a level 40-something farmer with all the friends and neighbors I needed.  But at a certain point, it just stopped being fun and entertaining.  The rewards weren't within reach, and the tasks became chores. 

It interrupted my life without adding anything to it.  And therein lies the challenge of a platform built on game dynamics with limited real utility.

In the short term (one year) Farmville has been a smashing success.  But in the longer picture, how much will users really continue to care about being the mayor of the coffee shop, or an astronomically high level farmer?  At a certain point, the rewards will appeal only to a dedicated group of aficionados, while the rest of the world will go on humming.

Blizzard Entertainment has done a great job maintaining and growing their deeply engaged community on World of Warcraft, in part by continuously adding richer engagements and new opportunities. 

Do any of these platforms demonstrate long term viability in their current state?

At a certain point, even the behemoth of a driver that is the combined social and game dynamics runs out of steam.