If every American saved the rebate and invested it in equities, we might be (ever so slightly) better off. Government can borrow at a low interest rate for us. Of course we’re being told to spend the money.
Most fundamentally, more aggregate demand is not the answer because insufficient aggregate demand was not the problem in the first place. … The economy is undergoing a sectoral shift toward less risky assets and that can bring an economic downturn. The shift itself is costly, it brings thorny coordination problems (e.g., sudden insolvencies, overturning of credit expectations), and lower-yielding assets also mean less wealth. Lack of liquidity simply is not the fundamental problem.