YouTube - Fstoppers Original: The Stolen Scream.
Personally, I think it's a pretty cool story because it worked out well for this guy.
I, of course, think that you must give credit to the photographer, but basically posting to flickr is a form of marketing. You get way more random views on flickr then you are going to get on your site. One of the risks you take is that you are going to get ripped off. But, if you are at all serious about being "a pro" (like you are depending on your images for your livelihood) you aren't posting you stuff to the net before it gets sent around for editorial review. And I don't buy the argument that this form of image stealing is going to put the big photographers out of business. They have to be pushing the boundaries all the time and furthermore it's less complicated for big publications to just shell out the money for licensing up front than to risk being sued.
I'm not saying that it is right to steal these images, I'm just really tired of this over-protectionism attitude for photos. I think few people realize that by wrapping their site in flash they are shooting themselves in the foot when it comes to SEO, not to mention the fact that you are excluding visitors. People need to have some savvy about what they are posting. Beyond that you just need to trust people to do the right thing. If it ultimately goes truly viral, then you just got your break like this guy.