As far as tax "rebates" to those who aren't paying income taxes to begin with, I think most economists agree that you get a greater stimulus bang for your buck of government spending when you put money in the hands of people who will be almost guaranteed to spend the money quickly.  That's the whole idea behind tax credits to the working poor, or for that matter stuff like extensions of unemployment benefits.  These kind of policies may not appeal to the average American taxpayer's sense of fairness, but they appear to have a fairly solid economic purpose in a period of recession.