ETA - the biggest problem I actually have is with what other parents allow - what are they going to be doing when they are elsewhere? and the 'but she caaaaan' argument gets realllly old.
That's the problem I have, when DS has a friend sleeping over they are not allowed out after dark but I do know of other parents who allow them to leave the house .

Regards,
Dianne
IKWYM! I'm lucky in a way that I know DS's closest friend's parents and we're on the same wavelength, but there are a few friends we aren't close to and that's where things start to get a little frayed. And teenagers are great at making you feel like the worst person on earth!
I just try to go with my best judgement at the time for the given circumstances, and hope that the "fringe" friends don't become too regular