Photo Blogging for Cash?

I have noticed a ton of photo blogs out there and was wondering what kind of cash they were making. Using only their digital cameras and micro sd cards they seem to have been popping up all over the place. Using places like Flickr to post their photos, and share them, or just plain displaying thme on their blogs.

Is this a new way to make money on a hobby? The hard part I would think is to get relevant ads on your sites with out any content other than photos. Good SEO people at least label their photos in the code that may help, and have good titles, but how would you keep the ads relevnant? Seems pretty simple to me. Every post would have the word "Photo" in it from my perspective. "Photo #12: A Beautiful Day", for example would amke it so Phot was probably the most used word on the blog and in turn make all the ads relevant to photography.

Hmmm...maybe I should make one.