This Video shows, a photographer finding her work copied from internet and as a print in T-shirt. However this is just one photographer finding out that her work is used commercially without her permission. The number of photos copied of the internet without the photographers permission is remarkably high but the number of photographers finding their work being copied and ised without their permissions is incredibly low.
Of course the Flickr didn't have anything to do with this photograph being used without the permission of the photographer, however it acts as a vast cyber space where browsing and downloading high resolution photographs are made easy.