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. The site launched in February of 2004, and has since become the most popular social site on the web.

Facebook continues to impress with continued explosive growth with an estimated 500 million users in July. Look for launch of "Facebook Stories" where users can share how Facebook has impacted their lives.