Incompetent staff, dangerous lack of maintenance
Upon checkin, was assigned a ground floor room (not preference, but ok); upon entering room, discovered slider doors (to outside) did NOT lock (broken). Keep in mind that this is Fisherman's Wharf area which is tourist area BUT also has its share of crime like any downtown area. 
Back to front desk; tell them I need to swap rooms. They move me to another room.
Move into new room. Decide to call it a night and go to bed. 
Get woken up at approximately 1130pm when strange guy is trying to get into room. Call front desk about someone trying to break into room. Front desk says, "Just ignore him. He's prob drunk. He'll go away.". At this point, I can't believe what front desk staff is saying.
Strange guy is still trying to get into room and is banging on door now. Call front desk again. They FINALLY decide to send security. Security guard shows up and turns out the strange guy was another guest who had just checked in.
Front desk gave him passkey to MY room.
Security guard tells him some mistake happened and escorts him back to lobby.
Next morning: Met with manager. He said 'sorry'. It seems staff screwed up (obviously). I asked, "Don't your computer systems show a room is already assigned???".