Identity theft prevention services do not exactly prevent identity theft. They simply make it much harder for thieves to use the personal information they have stolen, thereby protecting you against many of the techniques identity thieves use.
We give away personal information all the time. Any time you write a check at the store, charge airline tickets, rent a car, mail your tax returns, change cell phone service providers, or apply for a credit card you are giving away bits of personal information, such as your bank and credit card account numbers, your Social Security number and your name, address, and phone number. These bits and pieces are a treasure trove to an identity thief. Once thieves have this information, they can use it without your knowledge to commit fraud or theft.
For example, identity thieves can take your personal information to redirect your financial data, such as bank and credit card statements, to prevent you from noticing that your existing credit card or bank account is being used without your knowledge. Identity theft prevention services prevent this from happening. This doesn't mean, of course, that a thief couldn't have charged things on a stolen credit card, only that you would know about it sooner...assuming you check your monthly statements.
Protection services also prevent new accounts from being set up by identity thieves in your name. This protection is important because the only way you would know this had happened was when you began to be harassed by collection agencies or when you try to get credit, only to find your credit rating has been trashed.
Identity theft prevention services also help you should the thieves be successful, in that they will help you with the police regarding warrants as well as assist you with getting collection agencies to stop harassing you for debts that aren't yours.
If you think that you don't need these services because, after all, if you report your credit cards stolen, you won't get charged for the bogus charges, think again. Identity thieves don't just use credit cards. They can set up new cell phone accounts in your name. They can take out a car loan in your name. They can give your name should they be arrested then, when they don't show up at court, a warrant is issued in your name!
Identity theft prevention services are inexpensive...generally around $100 a year per individual or $150 for households. If you aren't a careful type, guarding your personal information, reading your statements carefully and noticing if they don't arrive, shredding mail with identifying information, then an identity theft prevention service might be right for you.