IMO, all that matters is that we can safely put cannabis in the "use in moderation" category along with alcohol, caffeine, nicotine, ibuprofen, and loads of possible carcinogens the jury is still out on. Unless prescribed by a doctor, the only thing you should safely inhale is fresh air, and people generally know that.

I hate that the legalization discussion is twisting into "well how safe is it?" If you're really concerned, don't use it unless medically necessary, or take your chances on other drugs which have plenty of known side effects. Just because it can be abused, or may not be safe in heavy dosages, is no reason to jail someone. Pertaining to regulations, I see no reason to extend beyond the current recommendations for alcohol - use in moderation, don't use pregnant, don't drive while impaired, etc.