The CrimeScene Blog ran a letter sent to them from a Monrovia resident concerned about someone unlawfully accessing checking accounts by use of debit cards/PIN numbers. The letter does not give much detail but it sounds similar to "skimming" which can take place right under your nose when making purchases, paying for a meal or using an ATM machine. Restaurants are used by suspects who carry handheld skimming devices to trap credit and debit card magnetic information. The suspects are many times the server of your table. Some restaurants have actually gone to use of portable card readers so that the transaction can be performed at your table, directly in front of you. This type of device helps to secure the transaction for your protection.
There are many resources on the web that give you information on this type of theft and fraud. Read the Wikipedia entry on the topic and it will give you some insight and topics to query. Here is another link to a helpful website, "Bustathief", where they actually have photos of modified ATM machines and what to look for to prevent your information from being taken.