Why does the Watchtower Society, Jehovahs Witness headquarters, discourage members from being on this forum?

Could be they don't want them to be exposed to other religious beliefs, One would think they would want them to come here and preach, they go do it most saturday mornings. But then again there is a lot of opposition on this site. Who knows my friend growing up was a Witness she said she was not allowed to have a Smurf doll, apparently they were evil...according to her in a meeting one kid once brought there smurf doll and half way threw the meeting the doll got up and walked out. I have had two witnesses tell me this now. They fully believed it as fact. Ahh well to each his own.