It is not mandatory because, as I said, there will be small and medium sized businesses that will not have the capacity to take on the automated method. For example, some minor sports organizations might send out a message twice a year. They just have to check their list before their next send out. In any event, they have 10 days to remove from the list the names of people who do not consent to receiving these messages. This seems perfectly reasonable to us. What is more, 10 business days was the number the committee arrived at when it was studying the bill the last time.
On November 2nd, 2010. See this statement in context.