Facebook was about sex from the start.

It might not seem that way today, between your grandma's inexplicable comments on the page for Applebee's and those extended musings on the sorry state of our politics these days from the high school classmate you never much cared for. But Mark Zuckerberg's first site was Facemash, a "hot or not" girl-ranking haven. And when Facebook itself debuted, thefacebook.com didn't have photo postings or groups or all that much else. It had only profiles, and on those profiles was something that lured in university students across the country: relationship status.

Washington Post