Along the lines of what's been discussed regarding this recent use of CheckUser results...
Let's say that you're part of a big city's police vice squad. In the course of some investigation of an unrelated issue, you happen to stumble on the customer list of a house of prostitution. There are no current plans to prosecute that place or its customers, and no active search or arrest warrants regarding it, but you get a glance at the list by chance while investigating something else entirely, and you happen to see that a prominent politician who's just starting an election campaign is on that list. Would you keep this information to yourself, or leak it to the press in an attempt to torpedo the guy's election? Just wondering...