The exact birthdate of the Internet is difficult to pin down, but it’s fair to say that it took at least three decades for the net to reach a population of that size.

Today, after just eight years in existence, Facebook now has more than 750 million users all by itself. At that astonishing rate of growth, the company is on track to accomplish much more than just a multibillion-dollar IPO. Facebook is on the cusp of becoming a medium unto itself—more akin to television as a whole than a single network, and more like the entire web than just one online destination. The evidence for that transformation goes well beyond the sheer number of users. Many businesses now bypass the traditional web altogether, limiting their online presence to Facebook. Already the platform has spawned one billion-dollar company (the social gaming giant Zynga) and swallowed another (the photo network Instagram). The average time people spend on the site has increased from four and a half hours per month in 2009 to nearly seven hours—more than twice that of any major web competitor.