SAN FRANCISCO (Reuters) - Facebook filed on Wednesday to raise a targeted $5 billion in a hotly anticipated initial public offering, setting the stage for Silicon Valley's biggest-ever IPO. Here are some key facts about the company:

Founded: 2004

Original name: thefacebook.com

Headquarters: Menlo Park

Employees: 3,200 as of December 31, 2011

Revenue: $3.71 billion in 2011

Founder and CEO: Mark Zuckerberg

Earliest investors: PayPal co-founder Peter Thiel invested $500,000 in 2004, followed by Accel Partners, which invested $12.7 million in 2005

Biggest stakeholder: Mark Zuckerberg, who holds a 56.9 pre-IPO voting stake Other top stakeholders: Greylock Partners, Meritech Capital Partners, DigitalSky Technologies; entrepreneurs Reid Hoffman, Mark Pincus, Sean Parker

Number of users: 845 million active monthly users worldwide, including 161 million active monthly users in the United States

Average time spent on Facebook: Worldwide users spend about 6 hours a month; 7 hours in United States

(Reporting by Sarah McBride; Editing by Gary Hill)