I'm squarely in the middle myself, I enjoy being by myself for periods of time working on my own stuff but after a while I need to socialize, and when I've socialized I need some me-time again :)
I just hope people think they're introverted because they lack social skills, being uncomfortable and not enjoying certain social situations doesn't mean one is introverted it only means one has to improve one's social skills.
They're like any skill, something you learn by experience and practice. Perhaps the reason that people think many computer-oriented people are introverted is because they choose to spend time in front of their computer instead of interacting with people (irl) and therefore don't develop their social skills as much.