People like labels. I'm sure you've labeled yourself as either an introvert or an extrovert at some point in your life. Am I right?
I think we're sort of missing the point here though. Just like a lot of other things, people usually aren't just one thing or another (please if anything, remember this).
In terms of extroversion versus introversion, I fall somewhere in between, as do most people despite our need to label. The very center of this spectrum is deemed ambiversion, a term that I just recently learned.
I'll explain in terms of how this relates to me personally:
I gain energy from being around people. I like to go out, be around people, hang out with friends and basically be the center of attention every once in a while. But then, after I've done this for awhile, the need to recharge is almost overwhelming. I need to go home and not be around people for a long time to sort of recover, and again, gain energy. Then this drains me, leaving me with little energy, at which time I crave social interaction; it almost instantly can make me feel better. I'll have a headache and go hang out with friends to make it go away. It's a sort of strange paradigm.
I suppose balance is key everywhere.