If I were to claim that I had copyright of the photo, would that prohibit David Slater from using it until the courts had settled things? It is absolutely Wikipedia's prerogative to use a photo they believe they are entitled to use. Now, they do lose the DMCA safe harbor exemption by not complying, but that only matters if a court should hold that they're guilty of copyright infringement.
Point of clarification: Wikipedia isn't just using the photo, they are offering it up to others to use as part of their "collection of royalty-free images" (Wikimedia Commons). In a sense, they are acting as a distributor, not just an end-user.
