To me the only harm that seems to be the most noticeable is the mood swings potheads tend to get and their obsession with the drug. It seems unhealthy to me, yes there are benefits but at the same time I see many who use and abuse it and think they are going to convince everyone else to do the same. I agree more with the edible and applicable uses of the drug rather than the inhalants since the health benefits are more safely received and the whole drug party attitude keeps things from developing in the wrong direction. I have smoked myself many times but haven't in years because it really no longer interested me. That and I had been noticing a lingering high feeling that felt uncomfortable even after months of going without. And of course the damage to the lungs wasn't in my best interests since mine are already quite weak.
I see the benefits but at the same time it can be irritating. The smell is obnoxious, many spending money on what they can't afford instead of paying for responsibilities, etc.
All in all despite all that I would not mind seeing it legalized. And as well as see alcohol more regulated itself.