Facebook

There perhaps are two ways to think about the Internet — before and after Facebook. By now you know the story. (Hell, they made a movie about it.) Some Harvard students create a site to rank girls. It expands into a larger network of collegians, and Facebook in its early form required a college .edu email address to join. In 2006, it opened up to anyone age 13 and older.

Fast forward a few years and many billions of dollars, and Facebook is now a publicly traded company. Co-founder and CEO Mark Zuckerberg is one of the youngest billionaires in the world, along with co-founder Dustin Moskovitz (who's younger by all of eight days). Facebook is how we keep in touch. How we stalk our former high school classmates. How potential employers check out potential hires. How news organizations and public entities get the word out. How we play games. How we share photos and video. How we forget how to have real relationships with actual people. It's how we log into other websites, using our Facebook credentials.

Like it or not, Facebook, in the span of a decade, became one of the most important online properties we've ever known.

Will it continue to be so in another 10 years? We'll have to see. But for now, there's no escaping it.