Your credit score can be an indicator of someone stealing your identity. It can also let you know where you stand credit-wise and allow you to take appropriate action.
However, I do think the commercials are a bit alarmist and preying on the fear (albeit a very real one) of identity theft.
Because I live in Maryland, I am entitled, by state law, to a free credit report from each of the three reporting agencies annually. These do not have my score, but, having paid for access to that information some time ago, I have a good idea of where my number is thanks to my annual ability to keep an eye on my report. As I went through a period of bad financial management during college, I make it a habit to check my report annually if only to remind myself that I can
live w/in my means because my report looks a whole lot better than it did 15 years ago. It's a nice ego boost to see all those checkmarks under the "Paid on time" boxes in each creditor's section.
The real terrible thing about those commercials and the companies who offer this service is that it's rarely a one-time transaction; you get your present credit score by signing up for a service which helps you to monitor your credit on a monthly basis, usually to the tune of $19.95/month. When you call to cancel, they hard sell you on keeping it by offering a steep discount and then making you feel guilty and afraid to continue with the cancellation process by basically telling you that you're going to get your identity stolen if you don't keep an eye on your credit score. Add that to the fact that the person you're talking to usually barely knows English and you get to engage in an incredibly frustrating experience that I would not wish on anyone.