[B Dids]

If it's a male friend, you'd better ask first and be DAMN sure it isn't an issue.

If it's a female friend, I would be more liberal.

All I know is that you shouldn't nail your best friend's sister without telling him, and have the friend find out when he learns that you're paying for her plane ticket to fly to another country to [censored] you. I know a guy who lost his best friend pulling this, in part because he thought that somebody saying "ok" to "I'm going to [censored] your sister" in an AIM chat was permission.