[sliverstorm]

At least in the US, look on the bright side- the odds of anyone needing your marrow are low, so there would be no sense in a systematic harvesting of marrow prison-wide every month. Inmates already work in labor gangs. So, if you are a prisoner and you get selected, strike a deal and get out of labor gangs for a month (because you just earned as much as if you had been in a labor gang). It'd be a good thing to get picked!

[angelbob]

Maybe. Bone marrow donation is debilitating and really painful. I suspect not everybody would want to duck out on labor gang for it.

[gst]

Painful? At least in Europe this is done under general anesthetic and after the procedure you shouldn't feel more than light pains.