Daryl Lang of Photo District News has more on the Richard Prince lawsuit, mentioned earlier here.
Lang says the case "is similar to a 2003 lawsuit by photographer Andrea Blanch against artist Jeff Koons" for his use of "a photograph of a woman’s legs as part of a painted collage." Koons won that case, which I discussed here. I'm sticking with "astonishingly unpredictable" in this case.