Social games company Zynga has filed for an initial public offering of shares in the US. While the company has yet to set a price or total number of shares to be sold, it estimated proceeds from the IPO at US$1 billion in order to calculate the registration fee with the SEC. On the subject of mobile, the firm noted in a filing: “We have limited experience developing games for mobile platforms. We expect to devote substantial resources to the development of our mobile games, and our limited experience makes it difficult to know whether we will succeed in developing such games that appeal to paying players or advertisers.”