Good, Bad or Both?

While having a discussion with a friend of mine I started to wonder what EXACTLY makes a good girl "good" and a bad girl "bad." Are the definitions fairly specific, or is it all a matter of perception? To me a girl can be both good and bad. For example I am a good girl who likes to be bad when it is appropriate. I try my best to be the kind of person who is loyal, honest, giving and supportive. I hate to hurt anyone unless it is absolutely necessary to protect myself. Conversely, I like being a bad girl...The kind of girl who can make your head spin with a well timed phrase or a single well placed touch. I think I am a perfect balance of both worlds, but I was more than curious as to what my guys would have to say about the concept of good/bad; so I asked them for their feedback.
It seems most men believe in the concept of good girl/bad girl, but there are some interesting definitions as to what that is. One of my guys pointed out to me that a "good girl is all about perception, a bad girl just tells you how it is." I have to admit he has a point, most of the so-called bad girls I know have no trouble whatsoever laying it all out there with a "devil may care" kind of attitude. However, the "good girls" I know are more likely to worry about what someone will think of them and they do whatever they think is needed in order to been seen as paragons of virtue.
One of my guys also pointed out that he doesn't think there is a "grey area" in the good/bad category. He feels pretty strongly that you are either one or the other at heart and that is that. While I may not agree with his take on the situation I respect this because I have known some girls who were solely good or bad. In fact I have known many girls who were just plain out evil. While I can recognize that this type of bad girl exists I think she is a different type of bad girl from the ones I am discussing here. This kind of bad girl is out for blood because she has a deep hatred for herself, men, women or all of them as a whole. In the end this kind of bad girl just winds up hurting herself because she can never escape the misery she continually creates for herself. And on behalf of all of us women who are NOT psychotic and think it is totally wrong to stalk you or "boil your bunny" I apologize to those men who have had the misfortune of encountering one of these kinds of bad girls. They give all women a bad name, and we don't like them anymore than you do!
Ok, I am done with that little rant, so I should get back to my point here. I was also sent a definition that reflects my opinion that a girl can be both good and bad. It seems a good/bad combo can exist, and it is something like this: A good girl can be proper and perfect in public, but then she becomes a bad girl when you are alone with her and she is whispering dirty things in your ear. That's what I am talking about...A good girl with a wild side!
There were also a couple of traditionalists who pointed out that a good girl is who you marry, a bad girl is who you fuck hard. Now that throws me a bit because if a good girl is that good how much fun can she be to spend the rest of your life with...? Don't men typically want a woman they can take home to Mom AND fuck hard later?! Maybe I am just confused.... Please clarify this for me fellas!
I am neither an Angel nor a Devil, I am simply me- but I still wonder if there is a category for girls who are both. That is a question I have not been able to answer to my satisfaction. All I know for sure now is that Good Girls and Bad Girls do exist, and that most men aren't that picky about which one they go for as long as she is NOT psycho! Let me know how you define the two groups, and is there a grey area? My inquiring mind needs to know!