My experence has been that most... if not all redundant questions... come from people new to the rep scene. Im not talking about all new members of course..we have some awesome new members. But then we have those who are lazy and dont want to put the time and effort Into researching there subject. They show up just to purchase a rep...they contribute little if anything to the community. I think these are the folks that annoy us at times.
The block feature could be a useful tool with certain members. That being said...I also feel that this issue comes with the territory...unfourtunately