I'm also inclined to think of "dark matter" as this century's "ether," i.e. a mysterious intangible substance postulated to explain what otherwise seems impossible (in that case it was the propagation of electromagnetic waves through empty space).
It would help if they didn't call it dark "matter," since it also doesn't follow another basic law of "matter," namely that different objects can't occupy the same space at the same time. And if it does have such a gravitational effect, why doesn't it form into clumps, like ordinary matter?
Since in fact the only evidence there is of this stuff is certain gravitational effects, why not seek an explanation of these effects in terms of a better theory of gravity, or of spacetime? That would seem to better satisfy Occam's Razor, by avoiding the supposition of an insubstantial substance that can't be seen or felt.