Comment From a personal point of view: (Score 1) 73
I worked for DHS so here is my personal viewpoint.
This breech has huge implications. The first of which being that your 10 year background check covers EVERY aspect of your life, opening the way for those 4 million that were hacked to face identity theft. The info that is stored about your covers every single security question you might be asked to prove your identity. Mothers maiden name, check. Elementary school you attended, check. Every address you've lived at over the last 10 years, check - etc. The possibility of mass identity theft on a scale never seen before is very high.
Second, the data was so thoroughly researched and confirmed to be accurate that it could be used in such a way to create a National Security nightmare. ( Their should be some sort of scale for type of data stolen - this would be considered rich data) Since no rock was left unturned during your employment validation - i.e. foreign contacts, the cause of your divorce, and status of your relationship with said people - it would be extremely easy to create a false identity based on this information that could have up to Top Secret Clearance. Also, since the government is employing so many contractors at this time, one could use this false identity to work in some of the most covert programs in the US. (Look at the access Edward Snowden had).
Third, those whose data was hacked will now probably face increased scrutiny in other countries when (not if) this data goes public. For instance, if you have some sort of elevated clearance why wouldn't someone like (fill in the blank with a Nation that wants to cause issues with the US, Russia or China perhaps) question your reasons for being in their country? Your list of foreign contacts you give during your interview process might also be a risk in the near future if your status with the US government goes public.
