Alice- Actual receiver (Bob) is hidden
Bob- Actual sender (Alice) is hidden
When Alice sends an unusual amount of money and bob receives about the same amount
Keep the volume and commissions going.
When a small pool of customers send and receive a large amount of money it has an incentive to blackmail them and increase the commision.
Or if Bitlaundry decides to call it a day it could gobble up funds on the last day.