As a man, I have to say my experience is pretty different from what seems to be the general consensus.
1.I find I interrupt men more than I interrupt women.
2.I also find that men interrupt me more than women do.
3.I also find that occasionally I'm happy to let a woman interrupt me and then to listen to her because often when she does, she's sharing something emotional and/or personal, so I get to sit back and enjoy garnering some deeper knowledge about where she's coming from and who she is...
4. There's definitely a socio-sexual element to all this.
Even though I'm pretty ambivalent towards whether I'm talking or listening (unless the person has proven themselves to be a vapid fool, wherein I'm always warm and encouraging, and prefer to listen), sometimes I find, especially in a group of men, that men cut each other off pretty often, especially in the company of women. I'm not sure most guys I know are conscious of it, but it's the same way with all my male friends when we chill together, even without women.
It's always a competition: who can make the others laugh the most, who can do such and such activity the best. I honestly like it that way, but I think this male aggressive nature can lend itself to any situation, especially when the man in question is an extrovert.
If an extroverted man is hitting on a woman, he'll want to prove himself worthy of mating, so he'll want to maximize his opportunity to mate with said woman by persuading her of his value as a mate. He'll be visibly amped up and he'll want to share a distinguishing experience etc. Some women love that, while others are repulsed by it. To each their own...
I find that women can get competitive in a conversation too, but if it suits me to interrupt, I find it's easier to bulldoze over a woman's voice, which is less resonant and less able to generate force than my own. (I have an especially powerful voice though, which might negate my further observations in this paragraph) Women also seem more prone to "fold up" in a live argument. It stands to reason that perhaps women aren't necessarily less "competitive" in conversation, merely that they are more used to being bulldozed? The conflict, then, is that some women feel entitled to having their voice heard without retaining the ability to "earn" it by force.
Sidenote: I find that "good listener" is a trait that women generally seek but find to be rare. I hypothesize that this is because women recognize that listening for men is, at its core, a choice more than a forced reality.
I also find it is more common for a woman to seek a more profound sort of "sharing" in intimate (romantic or platonic) conversation. Because of this, women prefer to listen more than men do and for longer periods, if they are truly interested in the other. If a guy I know is listening to me, it's probably because I'm talking about something practical, like a way to improve on an activity we both like or a sport we both play, or else I'm making him laugh.
One man's observations.