What if Facebook isn’t so special after all?

As the fateful day of Facebook’s initial public offering draws closer, the giant social network’s financial results are attracting more and more attention. And while there are some blockbuster numbers in its recently updated securities filing — including a mind-boggling 900 million active users, half a billion of whom use the site daily — there are also some potential red flags, including rapidly rising costs for marketing and other expenses. All of this raises the question that investors will need to answer before too long: Is Facebook unlike anything we have seen before, or is it just another modestly profitable Web business?