i personally don't like dark matter/energy. it's simply something astro physics is using to get around the issue of 'there is something that we don't see, and especially don't understand'
we have a table of elements which we consider to be pretty much complete, all of them characterised by several numbers. if(!) we trust in the completeness of that table, then there is no reason to have an element that is not re-emiting light. unless you have can think of a physical system of an atom that has only a single eigenstate to its corresponding hamiltonian ... because then you could not excite it.
plenty of crap. in addition, if i recall correctly, they recently found a merged galaxy of some special sort: it would require dark matter to have that shape/form, but then it's special way of creation was up to now used to show that exactly those galaxies don't have dark matter ... sorry, can't find the reference at the moment.
and then there are plenty of examples of galaxies that have no dark matter and actually don't need it - in one example it seems that a cloud of hydrogen gas seems to do the trick ...
after all, i don't blame the astrophysicists. gravitational constant is one of the worst known constants you can think about (precision of about 10^-4).
from my point of view one should rather regard that whole 'dark something' stage at the moment as the first step to some new physics.