There is some controversy over whether or not to share your debit machine with a gift card program.  The answer is it depends.

Most debit machines can handle a gift card application and most merchant account providers over some sort of gift and loyalty card service in tandem with their credit card processing services.

The reason some business owners feel it is not a wise move to have gift cards on your debit machine is because rates change with credit card processing and having gift cards on that machine is a real quick way to be married for life with that processing company.  You can't cancel your services on debit machine if you have 100's if not 1000's of gift cards out there.  Those gift cards will only work with that service provider.

Gift cards can be very powerful and should not be avoided from using just because of this challenge.  You just should use a separate debit machines for each service, that way you are ever being held hostage by one service provider.