I'm not sure how things are done in the US, but here debit cards are the safest thing on earth. You can give the number to anyone - the only thing they can do is give you money. They'd need your card and your PIN code to be able to do anything to it - and there are a number of free numbers you can call to block your card if it gets stolen. You'll have a new card in the mail within days. If someone finds out what your PIN code is, it only takes another call and a few days later you can go to the post office or the bank to pick up a sealed envelope, read and memorise your PIN code and tear/burn the paper. Easier than pie. A lot easier than pi.