The two main issues with posts containing images hosted on non-
http://stack.imgur.com/ domains are:
Potential spam — in case the hoster replaces the images with advertisements.
There are precedents for both cf. Ban ImageShack images because they are reusing old URLs for advertising & What smart ways to prevent “image rot” can we come up with?. And in most cases, such posts don't contain proper attribution for the images either.
Say I come across such a post. What should I do as a user? Here are some options that come to mind:
Edit out the non-Imgur images, upload them to Stack Imgur myself and then replace the old image links with the corresponding Stack Imgur links. In this case, there might be some legal problems in case the image wasn't properly attributed in the first place and I'm not aware of what or whom to attribute.
Leave a comment on the post asking the OP to shift it to Stack Imgur themselves and provide proper attribution. In case they fail to do so within a day, then I go ahead and vote to close it and perhaps flag it. But in this case, I'm not sure what to flag it as. Even if I use a custom flag, the moderator might face the same dilemma as me. Moreover, Stack Exchange has repeatedly mentioned that it's not a moderator's duty to handle copyright violations.
So...what would you suggest?