Private vs Public - The Thin End of the Wedge.
I think I see a clear path ahead here, tell me if I'm wrong...
The police are public servants, paid for by taxpayers and accountable in the public view. Therefore their actions are noted and investigated in the public interest and for purposes of clarity. In theory, they should welcome this level of scrutiny as an opportunity to demonstrate how much we can rely on their sterling standards. I find it disturbing that, conversely, they go to some lengths to ensure that they are accountable to no one but themselves and use weasal-worded language to avoid scrutiny at every turn.
Same goes for MPs and Ministers along with their expenses, but only inasmuch as concerns their public dealings and accountability. I don't care if they like a bit of S&M at the weekends; if they once smoked a joint, if they own two jaguars or like duckhouses. I'm only concerned if taxpayers are footing (ahem) the bill, which makes it an issue of public interest.
Milly Dowler's parents? Not public servants, not accountable to us as they are our peers, and whilst their tale might be (morbidly) interesting to the public it is not automatically the case that their lives are therefore to be held as a matter of public scrutiny.
I dare say the same goes for so-called celebrities. You might be good at football or a fashion icon and some people might find that interesting, but that does not give us, as a society, carte-blanche to deconstruct your lives in minute detail.
By extension, that same right is not accorded to the newspapers, even if they do act as self-appointed guardians of our 'right to know'.