deducing someone's SSN

how to deduce someone's social security number [2]
  1. if you know someone's date of birth, and birth state, it's easy to figure out the first 5 digits of their SSN
  2. with some extra work, you can figure out the last 4 digits too

an academic study was done on this:

paid services

There are a few paid services, where a human will do some footwork (likely some of the above) to figure out the SSN.