I hate the idea that someone dealing weed in 12th grade gets nailed for a felony and a public defender and has his life ruined with prison time. It's a waste of taxpayer money and only creates a more serious criminal out of the guy than a better solution would.
That said, the violent criminals need to be penned up like the sub-humans they are. "But it doesn't deter violent crime!" "How can they ever re-assimilate into society?!" I don't care. Prison isn't to benefit them, it's to benefit the larger portion of society that doesn't commit violent crimes. It isn't the nation's fault that those who commit the crimes have a clear statistical trend.