I for one am OK with recreational and medical use. I think that the risks to society of adults using cannabinoids are fairly minimal. It certainly doesn't make people drive dangerously the way alcohol does. It does have a whole set of risks that aren't covered in this issue, and that really need to be kept high in our awareness as this drug becomes widely acceptable.
One risk that is coming into focus these days is of extreme overdoses. Back when folks just inhaled smoke, coughing stopped them from partaking too much. Vaporizers now make inhalation gentler and it is easy to overdose when consuming edibles. With either method you can't tell how much intoxicant is in there. With humans ingeniously extracting and concentrating the active principles, it could be very strong, or contaminated with solvents. With edibles the effect takes time to kick in. It is terribly easy to overdose for folks who are experimenting for the first time, and who have no tolerance at all.
The conventional media take on overdose--blaming it for many deaths and claiming that it is deadly--is probably overblown. It takes a massive amount of pot to kill, perhaps more than anybody is likely to actually reach because unlike opioids it is so unpleasant getting there. It is however a relative unknown: having been illegal for so long, we don't have scientific studies about overdose. We hardly have science to justify all the medical uses that have already been approved. We are going to find out now.
Another risk is incurred by the fact that edibles make the drug palatable to people who would never smoke it. It is tempting to children as candy. There is the danger that children, teens and early 20-somethings will enjoy sugary yummies containing cannabinoids and permanently alter their brain development. Later on in life there is still a brain changing effect, but in early life when the brain is still forming, the effect can be severe.
On top of these new risks due to the availability of edibles, there is the old risk of respiratory injuries resulting in sinusitis and bronchitis, and risk of more dangerous conditions like pneumonia and COPD. There is also the fact that marijuana increases heart rate significantly in most individuals. Folks who already have hypertension or heart palpitations might give themselves a heart attack.
I suppose my main message in the light of all this 420 excitement is BE CAUTIOUS and PROTECT YOUR CHILDREN because there is a lot we don't know. I believe in freedom and individual discretion as most Americans do, and I also know that people can be terribly foolish and injure themselves and others, especially when intoxicants are involved. I cannot protect the whole world from poor choices, but I do hope that this warning is heard widely. Please take care of each other and if you are going to play with the newly legalized products, start very small.