I remember an Australian talking about the various levels of clearance - confidential, secret negative (anything stand out in your history), secret positive (in-depth active examination of your history). He said that the process wasn't about finding dirt on you, it was about finding out if you had any dirt that could be leveraged against you. For example, if you were gay and being outed would be a problem, then that's leverage. If you didn't care and were clearly open about it, that's not leverage.
That harmonizes with my experience. I was interviewing for a "top secret" job with the US and spent some time studying the system and looking over the appeals rulings of the clearance process.
Generally, the key things were, "are you a crook? are you liable to be bribed/coerced?".
E.g. one chap was a transvestite, but the appeals court ruled that since his wife and minister knew, it wasn't something that could be leveraged against him.
