I just read the blog here about the lady who stole $5k from her PTO's scrip program. Anyone who has a scrip program should pay close attention to that case. It is extremely easy for a scrip coordinator to take advantage of the program for personal gain.
The scrip coordinator has control over purchasing hundreds, sometimes thousands, of dollars of gift cards on the PTO's behalf. Because the payment is automatically deducted from the PTO's checking account by the scrip company, the coordinator can order any amount of scrip, whether or not the PTO has actually collected money to pay for it. I bet that's what happened in the Wisconsin case. The coordinator probably just added a few cards for her own personal use when she placed the order with the scrip company.
As a treasurer in a scrip PTO, I can tell you it is very difficult to accurately match the automatic bank account debit to the money you take in from your scrip customers. There are shipping charges that are applied, and timing issues that just complicate the matching process, leaving the door open to intentional or borderline intentional ("I'll pay it back next month") theft.
Luckily, there's an straightforward financial control that will reduce this risk. You must have two (unrelated!) people run scrip. One person takes in the money with the orders and prepares a consolidated master order of which gift cards the customers have paid for. This person also verifies that the customers have sent in the proper payment and sends the cash/checks to the treasurer. Person #1 then hands the consolidated master order over to Person #2. Person #2 is the only person (besides the president and/or treasurer) who knows the password for the scrip company. Person #2 places the order only for the cards on the consolidated master order. Person #2 never handles any money and must send the master order sheet to the treasurer she can match it to the bank debit.
This doesn't guarentee security, but it's better than letting one person do it all in a vacuum. Even a normally honest person can be tempted to take advantage the PTO's trust. In our PTO, a former scrip coordinator owed the PTO $90 for cards she had ordered for herself. As treasurer, I probably wouldn't have ever been able to reconcile that discrepency (poor record keeping), but she mentioned it to me herself. She wasn't trying to steal, it was just convenient to order cards for herself while she was online purchasing the cards that other parents had ordered. It took 3 months for us to get her money.
Scrip is an AWESOME fundraising program!!! But you should ensure you have your TWO coordinator system in place so no one falls prey to temptation.