There are many such 'fight clubs', not just for geeks, although those are most likely to videotape and post it to Youtube, I guess. It happens in garages across Europe (I have no reason to believe it is different elsewhere). It's just tough guy talking, to have a story to tell in the bar or club. I've been to many and in most places people just stand around to look tough, but avoid any actual workout or training. Any halfway skilled muay thai or bjj fighter (as in, 1/2 year of serious training) can take on 90% of the people in those sort of gatherings. I mean I'm 5ft9 and less than 170 pounds and I've relatively easily dominated people 1 foot taller and 50 pounds heaver, and I'm not even a good fighter.

I've seen people get knocked out by accidental swings and hits, and people throwing up because the intense activity of a 1m30s fight was too much for them. Some nose bleeds here and there, but I've never seen 'serious' injuries, mostly because people have no kicking technique, no grappling skills (no joint locks or arm/leg bars) and telegraph punches from miles away. One dude broke his hand punching someone else on a a hard part of the jaw. I don't think it's dangerous, just stupid.