As Flickr says: "Flickr members upload more than 3000 images every minute, and yesterday yeoaaron uploaded the five billionth photo." As yeoaaron says: "I am Mr 5 Billion, and there ain't nothing you can do to stop me."
And just look at the URL yeoaaron's collage landed:
Beautiful! Here's to the next five billion, which will undoubtedly get snapped a lot quicker than the first five. [Flickr]