Investors have learned some painful lessons on the impacts of supply and demand from investments in once-hot social media stocks such as Facebook Inc (NASDAQ:FB), Zynga Inc (NASDAQ:ZNGA) and recent low hitter Groupon Inc (NASDAQ:GRPN), which analysts believe could hurt other Web firms considering an initial public offering. Zynga Inc (NASDAQ:ZNGA) moved down -1.96% with…