I think that the recent move by the WTS to reduce the contact between their 'publishers' and the public is a direct result of the public being better informed about issues such as the rampant child abuse and the WTS' cultic tactics. The WTS does not want the JWs to interact with the householder anymore because of the increasing critical attention that the media is giving them. The JWs are susceptible to hearing things the WTS does not want them to know.
By putting the JWs into public spaces such as campuses and subway stations and malls, the effect is twofold. They increase their visibility in the face of falling numbers and they insulate their existing members by reducing the public/JW discourse (in spite of the trolleys being set in public places).