I just want to chime in with a simpler answer. That's not really how Internet ads work. Ad deals between companies are fairly large and complex, at least the kind that are going to support a site like imgur.

Content is king and imgurs content is random and most likely junk. There's no consistency you could sell to a partner where'd they be willing to pay enough to allow something like DaringFireball does to work. The only way they're making enough is to put the junk we're dealing with now.