Exactly this. Everyone wants pics of our new baby, so we (my wife) posts new ones semi-regularly on FB. It's a super easy way to distribute them. But of course we have 2 relatives not on FB who INSIST we must send them pictures. Which means taking the time to find somewhere to print this shit, then mailing it off. Fuck you. Make a FB account - it takes 2 seconds jesus.
I've also found it's really good for inviting people to gatherings - either being the inviter or invitee. Way too fucking lazy to call up 30 people and play phone games. Plus, they forget the date or time? Hey go check your FB anytime to see.