Flickr's second billion took three months

The photo sharing site Flickr launched in February 2004. Yesterday the 2 billionth photo was uploaded to the site. The first billion took about 3 and a half years. The second billion took about three months. Now that's consumer generated growth!

I made the following chart based on when certain photos were uploaded to the site and double checked with my own photos to see that the dates matched reasonably.