  In most models of dark energy the structure formation stops when the
accelerated expansion begins. In contrast, we show that the coupling of dark
energy to dark matter may induce the growth of perturbations even in the
accelerated regime. In particular, we show that this occurs in the models
proposed to solve the cosmic coincidence problem, in which the ratio of dark
energy to dark matter is constant. Depending on the parameters, the growth may
be much faster than in a standard matter-dominated era. Moreover, if the dark
energy couples only to dark matter and not to baryons, as requested by the
constraints imposed by local gravity measurements, the baryon fluctuations
develop a constant, scale-independent, large-scale bias which is in principle
directly observable. We find that a lower limit to the baryon bias b>0.5
requires the total effective parameter of state w_e=1+p/rho to be larger than
0.6 while a limit b>0.73 would rule out the model.
