Parties don't really appeal to me at all, and I'd personally prefer not to meet other punters, even if we do all know why we're there.
As a counter to Pete's story, literally from the other side (as the same door was involved I believe):
I was on my way down the stairs after a punt one day, when there was a knock on the door (appeared to be completely unexpected). The girl I was with crept up to the spyhole and peered through to see who was there. She recognised them, dashed back to the room to get her phone, and gave them a quick call to ask them to disappear for a bit, so that I could leave. All sorted out, and it avoided the prospect of the neighbours seeing 2 punters passing on the doorstep.