• by Erik Sass , Staff Writer @eriksass1, December 16, 2011

The trading day isn’t over yet, but so far the IPO for Zynga, the social casual game juggernaut, has fallen flatter than wilted crops on FarmVille (okay, that was a stretch -- anyone got something better?).  After debuting at $10, the company’s stock briefly reached $11 per share before dropping to $9.28 at the time of writing, down 7.2% from the initial offering.

It’s not clear what’s behind the weak performance, but investors may be concerned about a couple things. For one thing, Zynga’s financial stability and profitability depends on continuing to produce Farmville-like successes, as interest in casual games tends to wane over time. For example, after reaching 80 million monthly users in January 2010, Farmville dropped to 60 million monthly users by September 2010, and 36 million monthly users by October 2011. While Zynga has been able to reproduce FarmVille’s success with new games like FrontierVille and CityVille, keeping the game machine running with new products will be a continuous, unrelenting challenge for the company.

Meanwhile the company’s financial statements are not entirely reassuring. In the first nine months of 2011, Zynga’s revenues doubled to $829 million -- but its net income fell 35% to $31 million. What’s more, the company remains heavily dependent on virtual goods sales, accounting for some 94% of revenues, which in turn are driven by the popularity of its games; if the hit parade falters, revenues will sink too. And despite attempts to branch out, it continues to rely heavily on Facebook as a distribution platform, tying its fortunes to the social network’s.

Whatever the reason behind its lackluster performance (so far), at least Zynga has good company among social media and commerce companies with weak stock market debuts. After a promising start Groupon’s stock fell below its $20 IPO price in the second half of November, before creeping back to $22.25 at the time of writing. Online audio service Pandora’s stock is currently at $10.34, down from an IPO price of $16. Only LinkedIn and Angie’s List seem to have done really well, with LinkedIn’s stock rising from $45 at the IPO to $65 presently. Consumer review site Angie’s List has done moderately well, edging up from $13 at IPO to $15.40 at the time of writing.