Facebook may be making an initial public offering by April 2012, according to a memo sent to potential investors. At the very least, they’ll have to start disclosing financial information by that time. This is because they’ll likely pass the 500-shareholder limit this year, at which point the Securities and Exchange Commission requires them to make their finances public. The announcement contradicts speculation that Facebook’s private share offering through Goldman Sachs this week was designed to keep their finances private. Once they bring more than 500 shareholders onboard, companies have 120 days to register as a reporting company, and they often decide to make an IPO if they’re already being required to make financial disclosures.