40. Facebook

Myspace was the first social networking site to truly go mainstream (sorry, Facebook), but there's a reason they got abandoned like a chubby girlfriend on prom night. It had less ads and spam, and the ability to customize content and actually work as a communications tool made the switch easy. "Facebook me," is commonly heard these days, a brand that is synonymous with social networking.

Mark Zuckerberg started Facebook's predecessor Facemash in 2003 by hacking into Harvard's computer network and stealing all the school's dormitory ID images.