Here is an article from Christianity Today about door-to-door witnessing:
http://www.christianitytoday.com/ct/2014/december-web-only/dangers-of-door-to-door-evangelism.html
http://www.christianitytoday.com/ct/2014/december-web-only/dangers-of-door-to-door-evangelism.html
...he argues that our current social-cultural moment has made the door-to-door model not only less effective, but potentially counterproductive. “Wave after wave of rationalistic, rehearsed (and at times coerced and confrontational) evangelism,” he writes in his preface, “has inoculated, if not antagonized, the broader culture.”