Joel said on March 22, 2011 at 4:03 p.m. Is the density of WIMP's that low? The last quote I heard was that 23% of the universe is expected to be dark matter, 73% dark energy, and 4% baryonic matter(Scientific American Nov. 2010). Putting this together with the fact that the probable LOWEST density of baryonic matter in empty space is about 1 hydrogen per 16 cubic meters, dark matter could than be supposed at least more dense than this in most areas of the universe. I think the problem is not that they aren't annihilating but that they might not all. An observation (semi-recent, 2008) of a bullet cluster collision (via Hubble) showed that when huge droves of dark matter collide they simply slide past one another as if unaffected by its counterpart and (not surprisingly) the collision itself. Each clump followed the trajectory the cluster would have had the collision not taken place and as if no collision took place amongst the dark matter clumps themselves. If density is the criterion for annihilation of WIMP's and they do compose dark matter this should have been a prime time for observation (the scientific paper on this collision even states dark matter is most likely collisionless). If this is a sound conclusion than production from high energy conditions may be the best bet(such energy would have to be much greater than that produced LHC however, as they have yet to detect traces of dark matter production), otherwise it's to the drawing boards.