The argument for a delay is that Facebook's plans are apparently changing because of internal interests. Facebook co-founder and CEO Mark Zuckerberg reportedly wants to wait until next September or later in order to keep employees focused on product developments rather than a pay-out. Some employees are supposedly keen to cash out in an IPO, but Zuckerberg wants to keep them around through next summer in order to complete certain feature rollouts. Facebook doesn't need to push for an IPO because it really doesn't need the money right now. The advantage of staying private is focus: you don't have to worry about investor phone calls or show up at investor conferences.
The argument against a delay is equally strong. Facebook may be motivated to hurry up the process in order to increase employee compensation. Early last year, Facebook put curbs on employees' ability to sell their company shares privately to other investors. To stop employees from quitting Facebook in order to monetize their shares, the company needs to go public so employees can sell their stock on the open market at various times during the year and cash in on their holdings.
Facebook's IPO will be most likely triggered by a section of the 1934 Securities and Exchange Act known as "the 500 rule" – once a private company has more than 500 investors, it must begin releasing quarterly financial information to the Securities and Exchange Commission in the first quarter of the following year. Facebook passed the 500-investor threshold this year, and so it will have to start publishing numbers in April 2012. Companies do not have to go public after publishing their financial data, but many do so in order to take advantage of market interest and momentum.
Facebook's valuation could end up being north of $100 billion, if it can manage to keep itself significantly ahead of the competition. When Facebook goes public in 2012, we will be able to put all this speculation to rest, though the argument of undervalued versus overvalued likely won't ever stop.