From Disney Cruise Line:

Due to the success of a pilot program on Disney Magic® and positive feedback from Guests, Disney Cruise Line® is introducing the auto-application of gratuities on all Disney ships.

The process will create a more seamless experience for you by automatically charging folios on embarkation day with the suggested gratuity amounts for the Server, Assistant Server, Head Server and Stateroom Host/Hostess.

Below are the effective dates:
• Disney Dream – Date to be announced
• Disney Fantasy – April 21, 2012
• Disney Magic – Already in place
• Disney Wonder® – April 22, 2012

You can add pre-paid gratuities at the time of booking or when processing final payment. If the pre-paid gratuities have not been added prior to boarding, you will receive a letter upon check-in explaining the automatic charge to their onboard account. You still have the option to modify or add additional gratuity amounts, or pay in cash, by stopping by the Guest Services Desk onboard.

As a reminder, a 15% gratuity is automatically added to any bar, beverage, wine and deck-service receipt.