If you call riding a bike at 900mph that could quite easily bend you over, butt rape you with a chain ring minus lube, and then give you bad aids just for shits and giggles 'dangerous' then yes they are.
But if you like doing that sort of shit then no, they're not.
I had a fight with my fixie last night, the fucker pinned me down with his forks and said lick my rim or else........scared? I was petrified.
hahahahaha