It's a well known resource, but definitely is under-appreciated. FNG doesn't just generate fake names or profiles, like other software, they actually make sense and are credible profiles. The addresses reference real streets that exist in the locations specified, with matching zip/postal code, and SSNs consistent with what would be issued in that area.
If you opened a stealth Paypal account and used the profile data from FNG complete with SSN, Paypal has been known to usually accept it. That can save you some trouble during a limitation, as PP may not then ask you for an SSN (since it's already been supplied). The matching info is also helpful if you want to indicate a certain ethnicity or type of name set (US names, Canadian names, etc).