That image is wrong and misleading.

Facebook: 140000000000 photos

Flicker: 6000000000 photos

Instagram: 150000000 photos

LoC: Wikipedia says 12000000 which is around the "Facebook has 10000 times more" so let's use that.

-----

Let LoC be a square of 1 pixel side lengths.

Instagram is 12.5 times as much. So the area would be ~13 square pixels, that leads to side lengths of 3.5 pixels.

Flickr is 500 times the LoC -> 500 square pixels -> square with sides of 22 pixels

Facebook is 12000 the LoC times -> 12000 square pixels -> square with sides of 110 pixels

As image: http://i.imgur.com/gCjqV.png

Ouch.