FWIW, I can't justify harsh penalties for selling something and light penalties for buying it and using it. It's the same voluntary, mutually beneficial market transaction, and it seems that both parties to it should be facing somewhat equivalent legal risks. I'm not accusing you of this, but this kind of disparate treatment seems justifiable only because for most people THEIR kid isn't the low life scum dealer, he's just a normal kid smoking a little pot.
Where I would favor harsh penalties is dealers selling to minors, or for that matter adults supplying it to minors. That's where we all agree the law should step in.