The newer US passports have an RFID chip in them that contains all of your personal identity information. Is there any sort of security risk that one should be aware of when traveling abroad? Can this information be hacked into?

Before the passorts were actually issued, there were concerns about individuals with the right software being able to read the information on the passports by using a nearby laptop. Is this true, or an urban legend? Does a passport require a metal lined case to deter this?