Is teacher guidance always necessary to become an expert? Is it necessary to have a teacher (or mentor/coach) to master every skill? What if I am taking an online tutorial with pre-recorded videos? Can I count that teacher training?

I have read the concept of deliberate practice and 10,000 hours of practice being needed to become an expert. But my question is whether these 10,000 hours need to be (partially) guided to receive personal feedback and/or coaching, or whether self-learning is sufficient?
I'll give you an example of a famous mathematician who developed his mathematical research in isolation. Arguably If someone manages to achieve a high level of skill in solitude for such an extraordinary difficult discipline as mathematics I would deny the need to have a teacher (in any case) to master a skill which is less difficult than be an expert in math. (Which is arguably any discipline). However as mentioned in the comments having some kind of feedback might be useful in mastering a skill faster. Additionally not every person is as gifted as was S. Ramanujan. Therefore I suggest it depends on your inborn intellectual abilities with regard to the skill you want to become an expert of. Therefore this question cannot be answered in general but only with respect to person X inborn intellectual qualities with regard to the skill person X wants to become an expert of.
http://en.wikipedia.org/wiki/Srinivasa_Ramanujan