Why many smart people are not social?

These sound like post-hoc justifications for introversion.

Introverts are introverts. Not all smart people are introverts, but the ones who are not social are introverts, and it's just their personality.

Yes, these sound like justifications for introversion because the society today thinks that everyone needs to be social.

I agree with you about the personality.

What an ad-hoc argument with a weak basis. Some people are just introverts, and many smart intelligent people are naturally deep thinkers who prefer solitude over noisy chatter at a pub. This can shed more light: http://www.ted.com/talks/susan_cain_the_power_of_introverts....

The power of introverts is a great talk. Thanks for sharing. I agree about the preference to the solitude part (one of the items in the blog post)

I think the internet is a great enabler for those with introverted personalities.

Some of the most introverted people I know are often quite active on social networks. For those people, sending out a tweet comes easier than speaking up at a party.

This is true too but during our surveys and interviews, we observed this far less than the other case which is to stay away from the social networks.