I never went to school for teaching. I've gotten a masters degree in education now but I will admit that it has done nothing to really help my teaching in the classroom. I had loads of experience teaching, but not in formal settings, prior to getting the job I have now and I think I am actually better off not having gone through a teacher training program.
I think schools should be allowed to decide who they think is qualified to teach. Ideally parents would be making these decisions along with students, but they don't currently have that option in most places.
The stranglehold on teacher certification maintained by most collegs is simply one of monetary interest, they provide nearly 30% of the revenue of universities in this country. Some people who go through them can teach and some people can't and I don't believe that they improve those abilities (though student teaching is a very valuable experience).