Because we all so often allow bank tellers access to our own personal accounts as their own personal use or "gift fund", riiiiight. Dana Samarelli of Secaucus who worked at the Hoboken North Fork branch siphoned off $541,000 from an elderly customer's account by pretending to help him set up bill payments as it was difficult for him to get around. When the FBI asked her how this might have happened she said it was a "gift". Samarelli is charged with with one count of bank fraud and another count of acting as a principal in the crime.
You can read all about Samarelli's scheme and how she worked it at the link above. Thanks Dana, for helping really keep the good name of banks and bankers going in this day and age.