He has violated the victims property rights. And initiated violence. The thief now owes the victim, his lunch + again + fear factor + capture costs etc.
“If, then, proportionality sets the upper bound to punishment, how may we establish proportionality itself? The first point is that the emphasis in punishment must be not on paying one’s debt to “society,” whatever that may mean, but in paying one’s “debt” to the victim. Certainly, the initial part of that debt is restitution. This works clearly in cases of theft. If A has stolen $15,000 from B, then the first, or initial, part of A’s punishment must be to restore that $15,000 to the hands of B (plus damages, judicial and police costs, and interest foregone).”
…
"But how are we to gauge the nature of the extent? Let us return to the theft of the $15,000. Even here, simple restitution of the $15,000 is scarcely sufficient to cover the crime (even if we add damages, costs, interest, etc.). For one thing, mere loss of the money stolen obviously fails to function in any sense as a deterrent to future such crime (although we will see below that deterrence itself is a faulty criterion for gauging punishment).
If, then, we are to say that the criminal loses rights to the extent that he deprives the victim, then we must say that the criminal should not only have to return the $15,000, but that he must be forced to pay the victim another $15,000, so that he, in turn, loses those rights (to $15,000 worth of property) which he had taken from the victim. In the case of theft, then, we may say that the criminal must pay double the extent of theft: once, for restitution of the amount stolen, and once again for loss of what he had deprived another."(6)
“But we are still not finished with elaborating the extent of deprivation of rights involved in a crime. For A had not simply stolen $15,000 from B, which can be restored and an equivalent penalty imposed. He had also put B into a state of fear and uncertainty, of uncertainty as to the extent that B’s deprivation would go. But the penalty levied on A is fixed and certain in advance, thus putting A in far better shape than was his original victim. So that for proportionate punishment to be levied we would also have to add more than double so as to compensate the victim in some way for the uncertain and fearful aspects of his particular ordeal.[7] What this extra compensation should be it is impossible to say exactly, but that does not absolve any rational system of punishment – including the one that would apply in the libertarian society – from the problem of working it out as best one can.” - Punishment and Proportionality - Rothbard
Soon, it should become pretty damn clear, that instead of robbing someones plasma television, getting caught and then having to work to the extent you essentially could have bought your very own plasma television, you now give that money to the victim. Even the dumbest criminal will begin to ponder, maybe I should just get a real job. Aye? Especially when in a free society, security agencies are going to be far more effective, and I’d say prevention would be a key factor as well.
In essence, the bum should get a job, or make funny signs that provide amusement to others who then voluntary give up their money to support the ‘artist’. [:)]