The fellow who uploaded this to YouTube writes:
This is possibly the most disturbing thing I've seen on the Interweb. I'm sorry for inflicting this upon all of you. PUBLIC SERVICE ANNOUNCEMENT: The mushroom in this video looks like Amanita muscaria, which are very poisonous! Don't ever try this at home, people. Picking and eating random wild mushrooms MIGHT KILL YOU. After a rigorous session of super-sleuthing, I was able to find out more about this guy. It seems that he is a performance artist from Japan that goes by the name of 'wotaken.' Here's his home page: http://katura.is.land.to/index.html.
YouTube Link (Thanks, Russ Gooberman!)