Oatmeal should sue. It's just not that complex to build image similarity algorithms that are robust to minor changes like photoshopping the link back to the outmeal's site out or resolution changes or image degradation from compression. At this point there's no real reason for FunnyJunk not to be permanently banning oatmeal's images from being displayed on their site after the first dmca except they don't want to and it makes them money not to do so.

Hell, I can build that for under $30K. Email in the profile.