I've seen plently worse.
What does 18 have to do with anything? From the looks of it, some of those guys could very well have been 18.
They were in a forest. They were friends. That weren't doing anything too crazy. The only stupidity here is no eye protection.
I'll see people much older than 18 do far more retarded things. 18 is just a number. Just like 16 and 19. They mean nothing in the reality of an aging person.
Here's a good example (which I nearly died after watching): www.break.com/index/dryicebomb.html