Absolutely. They do require a minimum deposit...which I think depends on the length of the cruise. If you have a balance left on the card at the end of the cruise, they'll issue you a check which can be cashed at the Purser's desk.
JW, Be aware though when you use cash the suggested tip amount for your entire cruise is automatically deducted from your account immediately (if auto tipping is applied on your ship). So if you secure your card with $250 cash and the suggested tip amount of $10 per day on a 7 day cruise is applied immediately you only have $180 in your account before you ever step into your room. Double that if you secure your card for your travelling companion too. So if you put down $250 cash for both occupants in your cabin your account will only have $110 in it.
If your run low on your cash deposit you will be stopped from purchasing anything until you put down more money towards you card.
You can also put down a credit card and then just pay the bill off in cash at the end if you want to avoid the long line at the purser's desk on the first day to establish the cash account. The credit card is only charged once at the end of the cruise, so if you have a zero balance nothing is charged to the card.
A credit card seems to work a little better then cash if your not the responsible type with cash. Thomas is right about the tip being put on the account. It doesn't leave much cash left especially if your drinking. Pop, water included.
On disembartion day they listed names and room numbers over the PA system of people to come down to the pursers desk to "Settle" they're accounts. There were quite a few but of course last week was the first of Spring Breakers. (Although there are plenty of irresponsible older adults.)
So based on the information on this thread, would it be possible to set up each of our pre-teen children with a S&S card with a pre-set spending limit, with cash (they've each saved $200 in spending money for the cruise)? We have prepaid their tips and they will each have a soda card as well.