  The linear growth factor of density perturbations is believed to be a
powerful observable of future redshift surveys to probe physical properties of
dark energy and to distinguish among gravity theories. We investigate
systematic effects on determination of the growth factor f from a measurement
of redshift-space distortions. Using N-body simulations we identify dark matter
halos over a broad mass range. We compute the power spectra and correlation
functions for the halos and then examine how well the redshift distortion
parameter beta=f/b can be reconstructed as a function of halo mass. We find
that beta measured for a fixed halo mass is generally a function of scale even
on large scales, in contrast with the common expectation that beta approaches a
constant described by Kaiser's formula on such scales. The scale dependence
depends on the halo mass, being stronger for smaller halos. It also cannot be
easily explained with the well-known distribution function of the halo peculiar
velocities. We demonstrate that the biasing for smaller halos has larger
nonlinearity and stochasticity, thus the linear bias assumption becomes worse
for smaller halos. Only for massive halos with b>1.5, beta approaches the
linear theory prediction on scales of r or pi/k>30Mpc/h. Luminous red galaxies
(LRG), targeted by the SDSS-III's BOSS survey, tend to reside in very massive
halos. Our results indicate that if the LRG is used for the measurement of
redshift distortions, f can be measured unbiasedly. On the other hand, if one
considers to use emission line galaxies, which are targeted by the BigBOSS
survey and inhabited in halos of a broad mass range, the scale dependence of
beta must be taken into account carefully; otherwise one might give incorrect
constraints on dark energy or modified gravity theories. We also find that beta
reconstructed in Fourier space behaves better than that in configuration space.
