It's also important to understand something about 'social games': Most of them are not social. They tend to be single or multi-player games that use social networks (mostly Facebook) as an easy way to drive player adoption. What the industry is calling 'social games' are more accurately described as 'viral games'. 

The focus of most viral game developers is maximising trends. Trends rise and fall quickly in response to player boredom, retention is king, and developers spend much of their time reminding players to play, to invite their friends, to post stories from the game to their profiles, and other activity designed essentially to not let the player forget to come and play. Viral gaming relies a lot on ways to grab or nudge players’ attention. Like any third party game publisher they are reliant on the benevolence of their platform holders (primarily Facebook) and the market conditions that their platform has engendered. 

This has resulted in predominantly short-term thinking. Viral game development is a battleground of very simple and usually cloned games, interruption marketing tactics, push-to-the-limit tactics to jog players into returning to play, and a lot of scrambling to be on the next trends as fast as possible. Viral game developers, such as Zynga, have little or no commitment to developing deep or rich game experiences because the market has not really rewarded that kind of activity. However that lack of depth is precisely the reason why viral gaming is showing signs of weakness typical in any runaway success. 

Zynga and the End of the Beginning