SAN FRANCISCO?The number of people using Facebook hit the 500-million mark on Wednesday, meaning one in every 14 people on the planet has now signed up to online social-networking service.

"As of this morning, 500 million people all around the world are actively using Facebook to stay connected with their friends and the people around them," Facebook founder Mark Zuckerberg said in a blog post.

"This is an important milestone for all of you who have helped spread Facebook around the world."

To celebrate, the California firm introduced an application that lets members of the online community "tell the incredible stories of the moving and interesting ways they've used Facebook."

Examples given by Zuckerberg included NATO Secretary General Anders Fogh Rasmussen jogging with Facebook fans during his term as Danish prime minister and a US woman using the service to battle breast cancer.

"Our mission at Facebook is to help make the world more open and connected," Zuckerberg said.

"Stories like these are examples of that mission and are both humbling and inspiring. I could have never imagined all of the ways people would use Facebook when we were getting started 6 years ago."