Facebook, the biggest social network in the world, now has over 1.5 billion monthly active users. According to David Kirkpatrick`s book The Facebook Effect, the company was a very popular M&A target in its startup years.As early as 4 months after Facebook`s inception, people with money and people representing companies with money began lining up to beg Facebook co-founder and CEO Mark Zuckerberg to take their cash and sell the company. Obviously, Zuckerberg turned all their offers down. But some offers were much more tempting than you probably realize.Meet the 10 companies that tried to buy Facebook back when it was a startup. In June 2004, an unnamed financier offered $10 millionFacebook, then called TheFacebook.com, went live in February 2004. Just four months later and prior to any outside investment, a 20-year-old Mark Zuckerberg fielded a $10 million offer from an unnamed New York financier."He didn`t for a minute think seriously about accepting," writes David Kirkpatrick in The Facebook EffectFriendster also tried to buy FacebookAccording to some documents Business Insider has seen, one early bidder for Facebook was Friendster.But the deal was dependent on Friendster raising another round before Facebook got big on its own. Never happened.In the summer of 2004, Google came knockingMark and his Harvard dorm-mates rented a house in leafy Palo Alto during the summer of 2004. It wasn`t long before "a couple of Google executives came over to see if there might be a way to work with or even buy TheFacebook," Kirkpatrick reports in The Facebook Effect.In March 2005, Viacom plopped $75 million on the tableDuring Spring 2005, Facebook (still TheFacebook) was talking to The Washington Post Company about an investment. Out of nowhere, Viacom offered $75 million to buy the company. Mark would have earned $35 million on the spot, reports Kirkpatrick.Instead, then Facebook president Sean Parker used the offer to haggle better terms out of the Post (which eventually got scooped on the deal by Accel Partners anyway).MySpace too wanted to buy FacebookIn the spring of 2005, MySpace CEO Chris DeWolfe visited Mark and his team to "put out feelers about possibly buying TheFacebook," Kirkpatrick reports. Zuckerberg, his president Sean Parker, and adviser Matt Cohler met with Chris, "but only because they thought he was an interesting guy and they were curious about MySpace."MySpace`s new parent company News Corp wanted Facebook tooIn January 2006, then News Corp digital boss Ross Levinsohn flew Mark Zuckerberg and one of his top advisors, Matt Cohler, to Los Angeles. Levinsohn wanted to buy TheFacebook, but he worried it might not keep up its growth."That`s the difference between a Los Angeles company and a Silicon Valley company," Mark Zuckerberg says in The Facebook Effect, "We built this to last, and these guys (at MySpace) don`t have a clue."Viacom came back in 2005Viacom hadn`t given up on Facebook yet in late 2005. Focus groups told them that MTV viewers were spending more and more time on the site. So that fall, Mark flew to New York to meet with CEO Tom Freston. Tom pitched all kinds of synergies between MTV and Facebook. Mark wasn`t interested."It was a no-thank-you meeting," a source tells Kirkpatrick.NBC met with Facebook in 2005Kirkpatrick doesn`t offer many details, but apparently NBC executives stopped by for a peek in 2005. Desperate, Viacom came back one last time in 2006.In early 2006, MTV boss Michael Wolf stopped by Facebook one last time. Zuckerberg told him he thought the company was worth $2 billion. A couple weeks later, Viacom sent Facebook a $1.5 billion offer – $800 million in cash up front, the rest a payout later.Facebook almost sold, according to The Facebook Effect, but it wanted a bigger upfront payment. Viacom`s CFO was nervous about paying so much for a company with such small revenues. The deal fell apart. Viacom never came back.