Funny thing about door knocking is that it can be very effective. I have a friend that has been in the business about 30 years and is very personable. Whenever he gets slow and needs a little business he goes out door knocking. If he knocked on your door you would love speaking with him, he's a real character and would make you laugh with his nedless supply of great stories. Every time he does it, he comes back with a couple new clients just as he has done for the last 30 years.
I don't doubt that it actually might be effective. It's not that I would be annoyed if one or two realtors did that. But there was a period when 5 or 6 would do that on the same weekend. It was as bad as the telemarketer that just wouldn't go away. I don't have a problem with experienced realtors that actually know what they are doing. It's all the amateur ones that don't know half of what they're talking about that really bugs me.