I'm completely okay with this.
Firstly when you're at that age your social skills aren't properly developed, so getting into a relationship can be constructive towards preparing them for the future; Especially if it ends badly, it will teach the adolescent how to cope with future trauma.
Secondly dating when young is exciting, so if in the future -I know this is very rare but- they encounter an untimely death or receive some kind of socially inflicting experience, at least they'd lived while young.
My third and final point is the fact that if two individuals want to be together, we as adults don't really have a right to separate them, in most cases anyway. Trying to intercept their relationship is halting their free will, and I'm pretty confident that if you alter a teenagers social life, it will have a much more negative effect than if you left them to cope and learn about these things on their own. Who knows, this person your keeping from them could make their lives much better than without.
However there are certain situations when the parent must take a stand, for example if your teenage daughter got involved with some crooks, it is unacceptable to have them with them; This though, isn't really related to dating, it's more about children and getting involved in crime, it will happen or not happen regardless of whether it involves dating. So to get back to the point, dating at a young age is fine in my opinion , any negatives that follow this are possible to occur without dating anyway: Such as abusive boyfriends, as you could get abusive friends, and so on. So I don't see the harm.
