I realised today that I could upload an image into the question box, and copy the web address, and delete the link from the question - and the image remains at that link. In effect, I could use SO as a hosting site, and some people may exploit this, and host less desirable images on the site - without anyone knowing, because they never posted the question.
Example image - uploaded at about 2100 BTC (2000 UTC)
Possibly bug?
SE doesn't sort of doesn't host the images, Imgur does:
from https://i.sstatic.net/
Also, it may be more likely that it checks if the links are on the SE sites, or how many request for each image there are before deleting them - so as you have linked that image, it may not be deleted.
Edit: From Imgur FAQ:
As long as images are getting at least 1 view every 6 months, they will stick around forever. After that, your image may be removed to create more space for newer images.
I would of thought Imgur would use something like this, as people can often upload pictures and then not link/use them - Imgur have to cope with increasing amounts of images, so they get rid of unneeded ones.
Also, on deleting pics:
From the point of of moderation then, SE mods may be able to log in and request the removal of images.
I answered this on Meta Stack Exchange at Potential to abuse Imgur?. The short answer is, we don't currently auto-delete, but because we could start doing that at any time, and given that you can get the identical image hosting with a free Imgur account where you would stay in control instead of us, the potential for abuse is low because it just wouldn't make a lot of sense to do it.
Logic would dictate that stats are being kept for files that are loaded and that files that do not get loaded after x minutes get removed.
