Hypothesis: most rabbits which are in good enough shape to notice are also in good enough shape to escape.
There simply aren't enough old? sick? rabbits to freeload to make the system break down.
Anyone know whether inexperienced foxes chase noticing rabbits? If so, this make freeloading a risky enough strategy that it wouldn't be commonly used.
Hypothesis: most rabbits which are in good enough shape to notice are also in good enough shape to escape.
That correlation can not (and need not) be counted on to make the equilibrium stable over a large number of generations.
Sweet, there's another Bloggingheads episode with Eliezer.
Bloggingheads: Robert Wright and Eliezer Yudkowsky: Science Saturday: Purposes and Futures