On December 16, 2011, Zynga, the well-known social network game development company, went public. This event followed other recent initial public offerings (IPOs) in the world of social networking companies, including Groupon and LinkedIn, among others.With a valuation close to US$7 billion at the time it went public, Zynga became one of the biggest web IPOs since Google. The recent enthusiasm for social networking companies raises the question of whether they are overvalued. Indeed, in the few months since its IPO, Zynga has shown significant variability: its market capitalization going from US$5.6 billion to US$10.2 billion, hinting at possible irrational behavior from the market. To bring substance to the debate, we propose a two-tiered approach to compute the intrinsic value of Zynga. First, we introduce a new model to forecast its user base, based on the individual dynamics of its major games. Next, we model the revenues per user using a logistic function, a standard model for growth in competition. This allows us to bracket the valuation of Zynga using three different scenarios: US$3.4 billion, US$4.0 billion and US$4.8 billion in the base case, high-growth and extreme-growth scenarios, respectively. This suggests that Zynga has been overpriced ever since its IPO. Finally, we propose an investment strategy (dated April 19, 2012 on the arXiv), which is based on our diagnosis of a bubble for Zynga and how this herding/bubbly sentiment can be expected to play together with two important coming events: the quarterly financial result announcement around April 26, 2012, and the end of a first lock-up period around April 30, 2012. In the long term, our analysis indicates that Zynga's price should decrease significantly. The paper ends with a postmortem analysis added on May 24, 2012, just before going to press, showing that we successfully predicted the downward trend of Zynga. Between April 27 and May 24, 2012, Zynga's price dropped 25%.