The possibility of you being scammed is extremely high unless you go through some sort of organization. But, really, a soup kitchen or something like St. Vincent de Paul would have people coming in. If these individuals wanted to give you their address then no one is stopping them from doing so (I doubt that the organizations would be permitted to just hand over addresses). Me? I would find it creepy and upsetting for someone to be asking me for my address so that they could send me charity.