According to a very short report by Reuters, social-gaming giant Zynga is preparing to file for Initial Public Offering (IPO) with the Securities and Exchange Commission this Thursday. The source was not identified, and Zynga has declined to comment on the matter. Zynga was recently estimated to be worth over $20 billion, and rumors of its impending IPO have been floating around for weeks. According to the latest rumors, Zynga will be looking to raise approximately $2 billion by means of the IPO.