Saw this while I was walking into the city earlier today - down in the bottom corner it says that the photo is from flickr.com/photos/chewywong.
I wonder if he knows that his photo is being used here (most of his photos seem to be using a Creative Commons Attribution license). Anyway - congratulations!
For clarification, this is an advertising campaign being ran by Virgin Mobile in Australia. There have been sightings of these billboards containing photos from Flickr in both Melbourne (Victoria, Australia) and Adelaide (South Australia, Australia).
There is a post in the FlickrCentral group about this photo - www.flickr.com/groups/central/discuss/72157600541608353/