I had to give credit card details for each of my adrs& we're on dining plan. It links in with the new cancellation policy.
It is to try & prevent no-shows as a $10 charge per person will be applied to the card in the event of a no-show. Cancellations have to be made by midnight the day before to avoid a charge.
There is a good thread about the cancellation policy on the restaurants board at the moment.
Hope this helps & if I've missed anything hopefully someone else will be along to correct me soon!