Surprise: some of the personal identifiers weren't accurate! Private investigators know this because we work with this data all the time. I would never take the information reported in a database as conclusive. How many times do we see multiple DOB's or SSN's listed for the same person? Let me count the ways...or for a good night's sleep, count sheep.
The error rate for basic biographical data (name, current address, SSN, phone number, date of birth) was 25% for ChoicePoint and 13% for Acxiom.Oh, this was an analysis of eleven, that's 11, people's profiles.