You'd be surprised. How much do you think Grant Gunderson gets for a Powder mag cover? More like $XXXX. and the first digit isn't 1 every time.
I'm sorry but a photo is a photo, and usage is usage. It doesn't matter whether its a blog post or the background on your web page, it is still internet use of the photo. It is his job, yes, and he could have not turned it into an internet spectacle. However, as a photographer, I am glad he did, because I will not even bother trying to sell Grenade an image, ever, because of the inconvenience it could cause me. He has potentially saved me and a lot of others from a whole shit ton of crap we no longer will have the possibility of having to deal with.