In a paper published online 25 October in the Monthly Notices of the Royal Astronomical Society, Moffat and co-author and Perimeter Institute colleague Joel Brownstein argue that their modified theory of gravity, which they call MOG, can also explain the Bullet cluster discrepancy. Einstein argued that gravity arises because mass warps space and time--he even came up with an equation for how the warping works. Moffat says he added "minimal" additional terms to Einstein's equation that subtly change how gravity behaves on galactic scales. The upshot is that gravity is stronger at these scales than Einstein predicted and that MOG can explain the gravity of the Bullet cluster without dark matter. Brownstein says he and Moffat have applied MOG to the behavior of more than 100 galaxies and more than 100 clusters, and in all cases, it has successfully predicted their motions "without the necessity of adding dark matter."
Of course, many astrophysicists are not convinced, so we will just have to wait and see how this turns out, especially with more and more observations being planned. Even the LHC will come into play at the search for the possible dark matter candidates.