Analysts have been reeling in shock from Zynga's most recent fiscal quarter results, as multiple firms react to the social game giant's "significant" revenue shortfall. Zynga saw revenues of $332.5 million for the last quarter -- while that's still an increase of 19 percent year over year, the figure disappointed investors, and Zynga's stock plummeted roughly 40 percent in after hours trading. Ben Schachter and John Merrick of Macquarie Securities Research admitted that the "shocking results and guidance raise our worst fears about the stability of the company’s business model and competitive positioning," questioning what exactly Zynga's sustainable competitive advantage is in the social games space. The pair added that in the mobile space, which Zynga is currently still trying to break into, the company "looks little different to us than a myriad of other casual game companies. "...At its core, [Zynga] is a marketing company, and it needs to prove that it can acquire and monetize users more efficiently than others if its casual games business is to grow profitably. "The bottom line is that Zynga over promised and significantly under delivered," they concluded. Colin Sebastian of Baird Equity Research noted that Zynga's revenues for the quarter were $10 million below the analyst firm's consensus. Zynga's active and unique users count did increase year-over-year, but largely due to the acquisition of Omgpop, suggested Sebastian. However, he added that, while Zynga's shares are now "in the penalty box," they should benefit soon from the expanding social and mobile games market. Cowen & Company's Doug Creutz noted that the results, which were "significantly below our street expectations," were due to deteriorating engagement levels for Zynga's games. In particular, Creutz cited the "underperformance" of Pictionary-like Draw Something as one of the main factors in the lower-than-expected results. "Given that Zynga earns 80 percent of its bookings through the Facebook platform, we believe at this point it is impossible to have any certainty on when growth in bookings might resume," he continued. He also questioned whether many of Zynga's problems come down to the fact that many browser gamers are simply moving over to mobile games, and hence leaving Zynga behind. "We are skeptical that Zynga's monetizing player bases on titles like FarmVille and CityVille, which have been around for years, simply forgot to play without proper prompting via their news feed," he said. "Rather, we think reduced engagement is due to a shift from PC-based social gaming to mobile gaming. We think this shift is likely permanent and ongoing, threatening Zynga's largest business segment."