OP was referring more to the idea of a bunch of random ass people coming together and doing a project with little no training or expertise beforehand.
Glue some foam together? eh, no big deal, one armed blind guy could do it.
Worst case? Get to spend time time washing off your hands.
Woodworking? Get atleast a hobbyist in there who has spent some time building stuff and knows how to properly hold the tool.
Worst case? Cut off a part of your body. Damage still limited to yourself.
3D printing/Metalwork? OK now you need someone competent, the risk of mistakes means serious damage to properly and people.
Worst case? You puncture a gas tank and turn it into a flaming rocket which explodes.