In general, keeping in touch with family and friends is an appealing thing to do for humans. The reasons for this are unimportant to the point but that it is a "fact" is.
In today's society, sometimes close friends and family are separated geographically by so much space it is difficult to keep abreast of daily events and thoughts or feelings that can change hourly.
Facebook allows me, my family and friends (or "Ex's"
) to communicate on a daily basis.
When JRex's mom was recently ill, for example, her entire family and mine too, were made instantly aware of all updates on her condition complete with any travel plans that JRex might have made during the entire ordeal. (assuming she elected to share them)
People can criticize Facebook with valid points and concerns. But for some people it is also an indispensable tool. Even if flawed by some details of privacy.
And YES, I managed to go through two divorces and maintain reasonable relations with BOTH ex's. who happen to know each other. 
