There has just been a study published in Science (Harvey et al., 2015) that is interesting because it shows the dark matter hypothesis is starting to contradict itself.
Harvey et al. have looked at the light from familiar objects like galaxies as seen from behind galaxy clusters, and looked at the distortion in the images due to gravitational lensing. They know what a typical galaxy looks like: a disc, so if it looks like a U-bend instead when it's behind the galaxy cluster, then they can infer the bending of the light that must be occurring and assume this bending is due to dark (invisible) matter in the cluster. They looked at 72 galaxy cluster collisions, and have modeled the collisions using several kinds of dark matter, and have shown that the only kind of dark matter that fits the observations, is a kind that doesn't interact with itself. I'd like to point out here that this makes the dark matter hypothesis self-contradictory since the dark matter particles have to be given a lot of kinetic energy (momentum) so that inertial/centrifugal forces keep them spread out in their usual orbital halo, but if you now imagine that two clouds of dark matter hit each other there should be a 'push' as the particles collide. This study proves there isn't any such push, so the simplest solution is that there is no dark matter. I'm sure someone will think of a way to make dark matter more complex to save the hypothesis, but it gets ever more ridiculous.
In contrast, MiHsC says that there is no dark matter (see my blog here and my paper here) and that the light is bending because its inertial mass varies due to the variation in acceleration within the cluster. I know the inertial mass of light is a controversial issue, but it has never been well understood, and MiHsC predicts galaxy rotation, cosmic acceleration, the flyby anomalies, the emdrive (light in a box) and many other anomalies quite well without invisible entities or contradictions (Introduction to MiHsC).
(Thanks sincerely to those whose online comments helped correct a technical error about dark matter that I made in an earlier version of this entry, but my original argument still stands).
Harvey D, Massey R, Kitching T, Taylor A, Tittley E. The non-gravitational interactions of dark matter in colliding galaxy clusters. Science 27 March 2015. Read more at Phys Org
McCulloch, M.E., 2012 Testing quantised inertia on galactic scales. Astrophysics & Space Sci., 342, 575-578. Preprint. Journal.