  Rapid 3+1D transverse plus Bjorken collective expansion in $A+A$ collisions
at ultra-relativistic energies is shown to reduce substantially the azimuthal
asymmetry resulting from jet quenching. While the azimuthal asymmetry in
non-central collisions, $v_2(p_T>2 \rm{GeV/c})\sim 0.15$ reported by STAR at
RHIC, can be accounted for by spatially anisotropic jet energy loss through a
1+1D expanding gluon plasma with $dN^g/dy\sim 1000$, we show that if rapid
transverse collective expansion of the plasma is assumed, then the asymmetry
due to jet quenching may be reduced below the observed level. Possible
implications of this effect are discussed.
