The fact that a substance is addictive does not make it, in itself, harmful. Consider water -- we're all hopelessly addicted. I challenge you to point me to any conclusive medical evidence that caffeine is harmful to your body. Although I agree THC is one of the more benign recreational drugs (alcohol is way more harmful than pot), I think it's silly to say that coffee or caffeine is way more harmful than THC, even if we just define harm as "effects which interfere with your daily life."