A good horseperson is responsible, respects their animals, has a quiet mature personality. Dares are the opposite of that. It's just stupid and not only dangerous (hey lets make a dare with this 1200lb animal that we don't understand and can't control that has lightening reflexes and potentially kill us both!! Yay!) but will damage your relationship with your horse. Treat them with respect please.
I like the idea of "challenges", safer and actually has a point.
They are horses not toys. Even your post "Don't tell me it's dangerous, I know what I'm doing" shows you don't.