Interesting post, I thought that I might add a word or two that may help define "it". Not everyone has the infamous "it" factor, "it" is different for everyone that has "it". Although it can best be described as presence.
There are commonalities that tend to run along the sexes, for women there tends to be a come hither quality without acting/dressing to evoke such a response. For men it is less definable. I have been told that I have the "it" factor and to the best of my reckoning it is more of a smoothness or suaveness(for me at least). I tend to not be an eloquent speaker, but when I genuinely compliment someone or pay extra or particular attention "it" comes out. I have been told by a good personal friend that whenever I do it to her she cannot often remember what I have said but instead remembers the feeling that my words provoke, and no she is not interested in me in any other way than being just a friend.
For me, the more genuine I am the bigger the "it" factor. However, both sexes do have people that have "it" and the best way of defining "it" I would have to come back to the idea of presence. People that really have the quality of "it", it is usually "on" all the time but it can be ratcheted up or cooled off,(at least by my understanding) it can be manipulated. I cannot do this because I can't manipulate anybody and tend to be somewhat oblivious but for people that can "it" can be a powerful tool for manipulation. Anyway I hope that that helped.