This is what Mark Zuckerberg said:
Tomorrow is Facebook’s 5th birthday. This is a happy occasion for Facebook, but much more significant to the Facebook team is the fact that over 150 million people around the world are using Facebook to connect with the people in their lives.
Facebook was founded in 2004 to give people the tools to engage and understand the world around them. We are glad and humbled that so many people are using Facebook in this way.