This will prevent Bob from sending you messages, friend request or from viewing your profile. They will not be notified. Comments on discussion boards from them will be hidden by default.
“O my God, teach me to be generous, teach me to serve you as I should, to give without counting the cost, to fight without fear of being wounded, to work without seeking rest, to labour without expecting any reward, but the knowledge that I am doing your most holy will.”
―
St. Ignatius of Loyola