I have been awakened by my door flying in, and several shotgun barrels in my face literaly. Police task force raided the wrong apartment complex. They were apologetic, and had a city handyman fix my door. It did scare the crap out of me. I had no time to react when they came in. I lived in a small studio apartment of a 4 plex. They did get the suapect they were after in the 4 plex across the street. I was not too happy. My apartment number was on the door.
Yes it does happen. Cops make mistakes about adresses. The thing is they are trying to use speed to keep the element of surprise, and usualy the officer, or informant that the info came from are not with the inital entry team so it is not that difficult in the heat of the moment to force entry into the wrong house, especialy if it is an aparment, duplex, or 4plex.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.