Take a moment and think about the time you explained what Facebook was to someone older than 40 years old. I bet it was difficult. I bet you heard, “Why does anyone care what I’m doing,” or “I don’t want people to see everything I do.” Now think about how many of those people have a Facebook page. The answer is probably astonishingly high.
Now just because your Grandma comments on all your photos does not necessarily translate into business value. But for every person that didn’t know they needed or wanted a Facebook page was a marketing opportunity for businesses.