This is probably one of the most disturbing Public Service Announcements I have ever seen.
I predict this will have the same effectiveness as when your parents asked you "If all your friends were jumping off a bridge, would you do it?"
Of course, that question always had the same answer. "I dunno. I guess."
Impressionable youngsters will always have a cavalier viewpoint regarding stupid things, regardless of whether those stupid things be drugs, extreme sports, gasoline cans, or sticking leeches on themselves. Simply calling it stupid doesn't do a bit of good, as most kids have not yet reached their age of mortality.
The young know they're going to live forever.
Older folks (meaning those past the font of wisdom that generally comes after turning 25 or so) know their mortality all too well.
So while pointing out the stupidness of various activities might seem to be a good thing from an adult/mortality-aware perspective, the simple act of pointing out the stupidest things that a young person could do will only accomplish one thing: make them wonder what all the fuss is about. Which will cause, I believe, only an increase in interest as to precisely what the heck all these old farts are babbling about which, in turn, provides for an increase in those attempting said stupid things. (NOTE: I believe this to be true. I have absolutely zero concrete evidence to back up this belief. Please read this parenthetical comment as a disclaimer to that effect.)
Listening to my adult nature, I see this advertisement and think "Damn. That's some pretty good thinking on their part. Kudos to Above The Influence."
Listening to my inner kid, I see this advertisement and think "Cool! I wonder where I can get leeches at 8:30 on a weekday!"