By the end of 2009, Facebook—under the control of its then 25-year-old CEO, Mark Zuckerberg—was clearly on the rise. It more than doubled its subscriber base during the year, from 150 million monthly active users in January to 350 million in December.
https://arstechnica.com/tech-policy/2019/12/why-the-2010s-were-the-facebook-decade/