Hi David

"Dark Matter" might be due to non-Newtonian gravity at low accelerations according to Bekenstein, Milgrom and McGaugh - MOND is the official name, and it recently gained credibility because Bekenstein has developed a relativistic version. Just what it means for cosmology is an open question for anyone wanting to apply Bekenstein's theories. Stacy McGaugh did a rough analysis and claimed it explains the peaks in the CMB better than cold dark matter cosmology.

"Dark Energy" observations - an apparent cosmic acceleration - could be due to an evolutionary effect in the type Ia Supernova light-curves used to infer its existence. Kepler's Supernova, which detonated in 1604, has recently been indentified as a type Ia because it spewed forth immense amounts of iron and carbon into the ISM. Core-collapse type II SNs keep most of the metals in their collapsed neutronium cores. If it was a type Ia then it was the weirdest ever seen and as a result it means that type Ia SNs aren't understood well enough to be the reliable standard candle of long-range cosmology they were thought to be.

Exciting times.

Adam