I find Facebook turns otherwise sane thirty and forty-something adults, into high school/junior high kids.
For her undergraduate psychology thesis, Mehdizadeh recruited 100 fellow university students and analyzed their Facebook postings...
The more prolific the Facebook activity, the lower they rated on the Rosenberg Self-Esteem Scale and the higher in the Narcissism Personality Inventory.
I have a massive family scattered all over the country. Facebook provides useful tools for keeping everyone posted and keeping track of everyone (and their birthdays).