Every social network or simple messaging program that you run as client on your PC.
In the beginning it starts as an innocent communication tool,
and later on , becomes as another door of worthless marketing spam.
I do have a profile on FB , mostly so to be tracked down from people who knows me,
than for new friends.
I had cripple all the ad-dons , and even limit my personal information up to a level.
I hate too the dating adverts .
Once one Girl from Africa had an crash on me, and send me a picture too . ( ICQ times )