As one link (concerning "electrical universe') provided earlier pointed towards...the very observations themselves which are used in the calculations, could well be themselves fundamentally skewed.
The question being is there such a thing as 'dark energy' or is there simply some wrong with how we're looking at things. Similar to how my old Chem1A prof complained about the 'neutrino', saying it was just a fudge excuse to cover up an error in the model. What we know now is that using the idea of neutrinos has come in pretty handy over the years.
We'll see how this 'dark energy' thing works out...