I think I filled out an SF85 or 86 once. I was 17 so I didn't exactly have much to declare, but now I wonder what can be out there. On the other hand, I haven't received any notification, so maybe it was actually a completely different thing I did.
Is anyone affected by this? Noticed any bad results so far?
For reference, here's the SF86: http://www.opm.gov/Forms/pdf_fill/sf86.pdf
So as we can see here, there's a lot of information in this form alone that you may not want others to know. I've heard reports that people who never even worked for the government have been notified that their data was leaked. All they did is apply.
After the form, there are personal interviews and polygraph tests, where you are asked things like whether you've ever engaged in bestiality, the results of which were also compromised.
Does the government really care about your sexual preferences? Not so much. But you might care whether others know about it, so when you get into a sensitive position and a foreign spy finds out about your escapades, now they can 'persuade' you to help them out with a little bit of information so they don't let slip... And this is what the government is worried about now.