I would imagine not too many instructors will be keen to have you film every lesson. Logistics of setting up aside, they'll be opening themselves up to all sorts of possible scrutiny from peers should it find its way onto youtube. I personally would happily accept the challenge however, we had this discussion amongst us instructors recently and I was a minority of one out of nine. The main objection was the distraction aspect, because there's bound to be some even if it's pre-flight... I guess they have a point really because once at the airfield your attention should be firmly on the objectives of your lesson and not worrying about what camera angle you're going to get etc... but if someone else took care of that leaving you, the student, to concentrate on your lesson I personally wouldn't mind.
VFE.