  We analyze scale dependence of redshift space bias $b$ and $\beta \equiv
\Omega_m^{0.6}/b$ in the context of the halo model. We show that linear bias is
a good approximation only on large scales, for $k<0.1h$Mpc$^{-1}$. On
intermediate scales the virial motions of the galaxies cause a suppression of
the power spectrum relative to the linear one, which differs from the same
effect in dark matter. This suppression can potentially mimic the effect of
massive neutrinos and the degeneracy can only be broken if the power spectrum
is measured for $k \ll 0.1h$Mpc$^{-1}$. Different methods to determine $\beta$
converge for $k<0.1h$Mpc$^{-1}$, but give drastically different results on
smaller scales, which explains some of the trends observed in the real data. We
also asses the level of stochasticity by calculating the cross-correlation
coefficient between the reconstructed velocity field divergence and the
galaxies and show that the two fields decorrelate for $k>0.1h$Mpc$^{-1}$. Most
problematic are galaxies predominantly found in groups and clusters, such as
bright, red or elliptical galaxies, where we find poor convergence to a
constant bias or $\beta$ even on large scales.
