The concept of karma

The concept of karma has entered Western societies pretty thoroughly. Especially in San Francisco, many people who are not Hindus seem to believe in the idea. Do you believe that harmful actions will come back to the person who performs them?

In Hinduism, this system of karma seems to imply strongly that life is fair since everyone is responsible for the results of their own actions. But how does Hinduism account for a) bad things happening to good people and b) bad people who seem to get away with their bad actions?