Patterns of Behaviour
How do you detect that someone has misused an information system containing personal details.
If you date someone who has a "Security" role, you will have your background checked as soon as the relationship is declared. If your past is seriously dodgy then your partner will be asked to choose between you and their job.
For those that have access to the systems, they are going to check you first, to save problems further down the line, not least being hurt. It's natural.
So if you check out a girlfriend, or have a mate do it for you, you actually won't get caught, as how do you determine a single lookup is wrong, without having someone vet every single lookup. The people who do get caught are those who systematically abuse the system with frequent lookups, or those who are stupid enough to admit they checked out their partner, and then dump them.
To actually police these systems to the level some seem to feel appropriate would take a huge amount of effort, and you probably wouldn't have any Police officers left. You only want to catch those misusing for criminally or fincially corrpt reasons, oh and those who use it as eHarmoney for cops.