Some people, including myself notice the 'direct links' information on some photos and start to wonder who is direct linking, etc to my photos.
It may be that part of the answer is easy...
Pick a photo in your gallery and bring it up on screen.
Now type in .jpg at the end of the URL and hit enter.
Your photo should now open in a window.
Go back to pbase and go back to that photo.
Voila - you now have a 'direct link' statistic on that photo that will never go away. So, it may be that in some cases it's not actually a bunch of active links sitting out there on the internet but instead it may be as simple as because of the above.