  Both observations and theoretical models suggest that the emissions in
gamma-ray bursts (GRBs) and the afterglows are beamed. We argue that the recent
polarization measured in the afterglows gives further evidence of beaming in
GRBs. In this approach, we adopted the polarization-magnitude relation of BL
Lacertae objects to 4 GRBs with available polarization measurements and found
that the data of the 4 GRBs are consistent with the relation of BL Lacertae
objects. This result suggests that the emissions in GRBs are beamed and there
are similarities between GRBs and BL Lacertae objects (or generally blazars).
We suggest that the weak polarization of GRBs may result from low percentage of
orderly magnetic field in the shock front.
