Is it not the case that when you use imageshack for posting graphs, others who are not registered with imageshack cannot see it? When I am not logged in to imageshack, all I can see is the frozen frog icon.

Is imgur different in that regard? Personally, I still use FTR to host my images. Go into profile then click "pictures and albums" in the menu on the left. It will let you upload your image and also give you a tag to use in your post.