  Acceleration of the universe might be driven by a continuous elastic medium
-- elastic dark energy (Bucher and Spergel 1999). Elastic dark energy can
stably support equations of state with pressure to energy ratio w > -4/3.
Stable expansion with w<-1 combined with an assumption of ``reheating of
elastic energy'' leads to exotic possibilities such as Expanding Cyclic
Universe -- an ever-expanding universe with periodically repeating inflationary
epochs.
