Clicked linked to this old Sex Drive post on rape in virtual worlds. Regina Lynn linked to this other post about rape in RPGs--the old-fashioned kind, with dice &c. I take the author's point, but I don't agree with it all. The main point on which I disagree is pregnancy. (1) An in-game pregnancy might be necessary to some plots. (2), and this is the greater issue, sex has consequences. They are always built in to our games. If you have sex, getting pregnant is a straight-up roll (or set of rolls). There's also a sub-roll for chance of twins (on 100% re-roll for triplets, etc--once someone managed to roll four 00s in a row on that one. Ouchy!), and if you're sleeping indiscriminately with seedy types, you have an STD chance. If you feel that these are violations of your character--well, you should know what your GM/campaign's rules are in terms of sexual consequences and outcomes before you have your character have sex. As for rape per se, I can see needing to make sure sensitive players are OK with that. We identify with our characters, we start to dream and think in character over a long campaign. We cry over their losses, much as some of us have cried when our favorite characters in novels or on screen are killed off. On the other hand, we do put our characters in these situations. And sometimes, in character terms, the very worst happening is the catalyst we need to do what needs to be done.
Also, the article in question references lovers being grabbed and held at gunpoint and other things, and saying even death is preferable to rape. Are we assuming here that most gamers, and/or their characters, aren't parents? I would submit to fairly horrible forms of torture before I let my son or stepdaughter be put before a gun. And for their sake, I would rather live through almost any pain--if you have someone, something, to live for, death is indeed the worst that can happen to you.
Of course, if in-game rape is used, the gruesome details should be left to the very thick-skinned. I'd propose another way of asking permission, I guess: "Is there anything that you absolutely will not allow/accept happening to your character?" Straight-up at the outset. If you live in an area where multiple groups are available, it might also be a good sorting process.
Virtual rape is another matter; for one, if the game has a built-in ignore feature, you might not have to deal with it. But it's possible that all the other characters see it and it colors their opinion (but doing it on a public channel or open chat may also get them banned for TOS violations)--it's personal, whether that's enough. I do remember a case where someone used a built-in feature that let them control other characters--I can't find the article I read, as it was some time ago--in a virtual house, and committed very graphic sexual acts between his own and another character. It resulted in a rules change where they had previously relied entirely on self-policing, if I recall correctly, and the banning of that character. At any rate, rape in most online games is not a plot issue. It's someone using someone else for sexual pleasure without that someone else's consent. This is the essence of rape, though I do not believe it so heinous a violation as a physical rape by half.