I don't think this is solely an old firm phenomenon.
Wasn't there a European referee who had to retire after a load of Chelsea (I think) fans turn up at his village looking for him?
I think Howard Webb's wife had people turning up at their front door after something that happened in the Euros a few years back?
Graham poll was sent Ariel photos of his house
Michael Oliver had people shouting through their letter box, and his partner had threatening/abusive text messages after her mobile number was leaked
Of course none of this makes it acceptable, but unfortunately, if people want to find your details then they will.
Either because they are readily available on a database or in a handbook, or because someone knows someone who can get access to your details.