According to recent reports, popular social networking site Facebook now has 500 million users.

The landmark means that Facebook presently covered around 8% of the planet's residents, just 18 months after it hit the 150 million user mark.

In June 2010, Facebook founder and CEO Mark Zuckerberg announced that there is a "good chance" that the social networking site could possess one billion users by the next 3-5 years.

The six-year old internet site has continued adding users at a record-setting speed in spite of rising worries regarding the privacy plans of a site, which owns additional data on its users as compared to any other website.

Facebook marked the milestone with the launch of a special segment in which users are prompted to register their personal stories about how Facebook has affected them.

In a video message, Zuckerberg said, "Half a billion is a nice number but the number isn't what really matters here. What matters are all of the stories we hear from all of you about the impact your connections have had on your lives."

"Instead of focusing on numbers, we want to help people around the world hear about these stories for themselves, and we want to let you tell your own story."