That's a common sentiment. Indeed, I hear people liken "I'm not on Facebook" to "I don't watch TV" more often than I hear people say "I'm not on Facebook."
I know it isn't a popular sentiment among hacker circles but if you stop to think, there are a lot of reasons to be cautious. Information about people has always been a precious commodity and now we're giving it away.
Another subtlety I noticed is this generation's concept of Self is becoming contorted into your number of 'Friends' and quantity of 'Likes'. Not really this intelligent HN crowd but, more so the other 99% of society that unconsciously uses fb.
Yes, us intelligent folk here on HN would never stoop to accumulate arbitrary, meaningless "likes" (or "points" if you will) based on some groupthink valuation of our opinions. And us hackers would never consider shaping our published opinions to match the group's thinking so that we could accumulate more of these..."likes".