Personal story about bias: I don't give money to people on the street, because I should only give to those who "really" need it, or who I am sure would use it "responsibly." But in reality, I'm inclined to give to people (white or black) who ask for money but don't look poor.
I guess it's in their interests, but I believe them; every homeless charity I've donated to says that giving money to folks on the street is a bad idea and often just goes on the next fix. Occasionally I just do it anyway because the need for a kindness seems so immediate. 