I've had a few unpleasant experiences in our current house - people collecting money/selling stuff being unimpressed with me because I refused (politely) to donate/buy. On two seperate occasions they shoved their foot in the door, shouted and tried to push their way in. On another occasion they returned to hammer loudly on the door 5 minutes later (and disappeared pretty quickly when DH answered the door), and I've had people hang around outside the house shouting once or twice too.
I don't answer the door after dark now. (we have no chain on the door, if we did I'd be happy enough to answer and use that). If DH is home, I ask him to do it, if he isn't I usually just ignore it.
Daytime doesn't bother me - although if I'm on my own at home in the day time, I get pretty grumpy about my peace and quiet being interrupted for someone selling stuff.