Jack Murray has written an article about identity theft that every genealogist should read. His article is not a re-hash of the old wives' tale of "your identity can be stolen online." Instead, he focuses on real-life scenarios: most identity theft happens in restaurants, grocery stores, gas stations and similar places where you personally hand over either a credit card or a personal check, along with identification such as a driver's license. You have just given the minimum wage employee on the other side of the counter all the information needed to impersonate you and to make charges in your name.
Other articles have pointed out that in-person identity theft is much easier to accomplish than doing the same thing online. Would-be con artists often take temporary jobs where they can handle credit cards, such as a retail clerk's position. Murray also points out the risks of giving your mother's maiden name to a bank or credit card company. Any institution that asks for your mother's maiden name to "identify you" obviously doesn't know much about security.
You can read Jack Murray's interesting article on the Marshfield (Massachusetts) Mariner web site.
By the way, when any bank, insurance company or credit card company ever asks for my mother's maiden name, I always reply "Fudpucker." Those companies really don't care if you give them your mother's real maiden name or not. All they want is an easy-to-remember code word that they can use to later identify you. Trust me, nobody is ever going to find my descent from the Fudpucker family on any online site!