I'm a bookish smarty pants and an introvert. My husband is way geekier, reads 200% more, and he's an extrovert. So I'm going to say no -- they don't have to be on the outside of social circles.

I think maybe being "aggressively" smart makes waves in social situations. I know I do this. Esp. if alcohol is involved. But I also love being around other people with big brains and ideas, we could go on forever.

Also some people are just flaky and that's nobody's fault. Maybe they're living with someone or married, then omg they're never going to meet you anywhere ever again. Or some people are just at and making and keeping plans. I wouldn't take it personally -- it's their loss.