When Mark Zuckerberg got his first bodyguard in 2011, it made headlines. But those days must seem quaint to the Facebook founder, who is now reported to have no less than 16 people protecting him at his $7million home in Palo Alto, California.

Zuckerberg is now so concerned about security that he has the bodyguards working in shifts day and night, a Page Six report says.

Though no reasons have been given for Zuckerberg's security concerns, the article does say that a number of Silicon Valley's leading lights are bumping up their security details due to threats from unstable website users.

Guarded: Facebook founder Mark Zuckerberg is often seen surrounded by security when out and about, but now he's protected by 16 bodyguards in his own home in Palo Alto, according to a Page Six report

An unnamed source is quoted as saying, 'You’re touching hundreds of millions of people. All the CEOs get threats, and they take them very seriously.'

If that's the case, then Facebook - which announced that it had 1.56billion users last month - may get more than most.

But it's not just web users who get angry - residents living near Zuckerberg's $10million house in Liberty Hill, San Francisco, around 30 miles from Palo Alto, have been complaining about his security detail in recent weeks.

In a letter written by one of his neighbors, Zuckerberg was accused of allowing his security detail to 'permanently' and 'illegally' occupy two prime parking spots in the area. A spokesperson for Zuckerberg denied that the parking was illegal.

Secure: Zuckerberg's Palo Alto house cost $7million, but he spent a further $30million buying up neighbouring houses in 2012 and 2013 to ensure his privacy. Now a roster of bodyguards has been added to the mix

Since he became internationally known, Zuckerberg has taken expensive steps to ensure his privacy.

In 2013, it was announced that he had bought four houses surrounding his own Palo Alto mansion for a total of $30million after he discovered that a real estate developer was planning on buying one of the properties and and advertising it as being next to Zuckerberg's house.