Since it's launch in February 2004, Facebook has become the most popular social networking site on the web.  This week, Facebook will reach a milestone of an impressive 500 million users.  

To celebrate, it’ll launch “Facebook Stories,” a visual memorial to all the ways the social network has changed people’s lives. Amongst the love stories and natural disaster reunion tales, it will be clear to see that the social network is no longer simply used by kids or peer groups - it has also become an important business tool.

Whilst previous announcements of the social networking leaders' milestones have been about the numbers, this time the company wants it to be all about the users.

This demonstrates the continued growth of the social networking site. People are now paying it the attention it deserves, and is has become the most cost effective way to do paid search and highly effective in reaching geographic and demographic areas.

Facebook reached 400 million users five months ago. This time last year, it had just reached 200 million and eight months before that it was at just 100 million. It's not surprising to see the social networking phenomenon has now become a key element of business strategy across the globe.