Not that I am much of a Facebook user / addict and have never used Twitter but at least FB has enough and more privacy options to circumvent the examples given above. Simply do not make your FB contents made available publicly and restricted to a small group who are your friends and whom you trust
I hv opted out of facebook/twitter......it was getting on my nerves and spoiling my peace till i rediscovered life with out facebook/google /twitter and any group blogs...i am now HAPPY...