How far is too far?
I expect culture may play a role in this as well as other groups.
My views (as an uncivilized westerner):
Generally, whatever you deal with should be true to itself in terms of what you should allow players to see and what THEY expect to see.
If you deal with a violent group then violence is what the players expect, not just a slap on the wrist.
Nudity, well, if it's tastefully done, provocative and true to the story that's fine but showing what could be termed as a 'porno' is I think too far for say AGS. EG: A fat, ugly woman in a nighty beckoning a young lad on could be conceived as 'provocative' yet 'funny'.
The people who love gore should be allowed, if warned, to view it in its true form. In games/films it is all pretend and no one actually gets hurt, most people are not that stupid.
If they WANT to see a guy get chainsawed then let them. An example would be a train going over someone cutting them in 3. If they are warned about the game content then it is their choice whether they play it or not.
Look at Quake, Doom and others like it, you go around blasting enemy brains out!! As in 'Hostel', the viewers who expect gore get gore in spades.
In this day and age the limits have been well pushed forward and not much is taboo, except stuff like rape,incest and bestiality etc.
Forewarned is foretold, they say.