Do you ever walk into an event – say, a party, a networking event, a bar, whatever – and not really know anyone, but know that people you do know will (maybe) show up, and then you see everyone talking to someone…and wonder if most people arrive at events with people they know so they don't have to spend a minute standing around by themselves looking for people they know?

Me neither.  Nope, not me.  Never.
On a serious note, I have taken the Myers-Briggs test three times (all forced upon me by various institutions, but of course, being a navel-gazer, I was a little interested), and each time I was smack dab in the middle on the scale of Extravert / Introvert.  This explains a lot.  And being an introvert, btw, does not mean you are shy.  It's about how you process information and how you generate energy.

I wonder if entrepreneurs are more often extraverts or introverts.  Are entrepreneurs born or made?  Is there a real personality type?  Can you spot it a mile away?