excellent question... I would say if i had to guess about half of the members here either occasionally visit exposure sites or occasionally search for effects on youtube.
I know that when i started i went to LMT but i didnt really know any better. But had it not been for places like that i would have never gotten stayed in magic, thus i would have never spent any money on the art. I think that if you go to these sites, you will eventually get to the point where you are too good to really get much from them, then you go and pay for things. If you never plan to expand past that, then you most likely never would have paid 30 dollars for a DVD.
So i think that most beginners go to those sites for a little while. The only people that you hear say anything about it though are those that are hardcore against it. and if anyone does speak up about doing it their voice is drowned out by all the others bashing them. I think they have their purpose in the art, and i know that they have had a positive impact on me as a magician.
Just my thoughts on the subject.
To be clear, i dont go to LMT or any other exposure sites, as i said i feel that after a while you just advance past it and realize its worth the money for the real version.