My best guess is that they are waiting to book an entire year of platform revenues - which will give investors a better idea of what their business model actual

My best guess is that they are waiting to book an entire year of platform revenues - which will give investors a better idea of what their business model actually is. This time next year they will have 12months of ads + platform revenue to show off. Their business model hasn't been complete up until now. That is why they opened and sanctioned the secondary market, because of employee pressure and because they had to buy time before going public. Besides companies prefer to remain private, esp because of the amount of overhead being public adds (esp after Sarbanes Oxley). The role of CEO completely changes when you are a public company. If anything the reluctance to go public is a good thing, since it means that Facebook are thinking it through and establishing themselves - not making a dash for cash. Google was also very reluctant to go public, but the SEC and their own employees forced the issue. This is going to be one hell of an IPO.