I haven't owned or even rode a bike since like 1988, and this is just another reason to keep it that way.
When I was a kid, I was riding my bike and thought it would be cool to pop a wheelie. Well, the front tire apparently wasn't on there all that tight and as soon as I landed, the front tire flew off. Not only did I do a sweet faceplant, I also slammed my balls into the handle bars. This is a painful memory that will live in my nutsack forever.