  We show that the string bit model suffers from doubling in the fermionic
sector. The doubling leads to strong violation of supersymmetry in the limit
$N\to\infty$. Since there is an exact correspondence between string bits and
the algebra of BMN operators even at finite $N$, doubling is expected also on
the side of super-Yang--Mills theory. We discuss the origin of the doubling in
the BMN sector.
