'I slept with Keira Knightley'

Such an event is, probably, an example of what one would brag about - in public or within a close circle - rather than keep secret, unless you are married with kids and don't want to come across as unfaithful and untrustworthy. (My choice of the "target" was inspired by Jeremy Clarkson who regularly refers to KK when talking about cars).

What is a secret when it comes to information we voluntarily provide about ourselves? Does privacy really matter?  

I can understand why secrecy is extremely important when it comes to business; even then the downside of exposure can, in most cases, be contained. What is the worst outcome of "secret" private information being obtained by the government?.. After all, neither WikiLeaks nor Snowden shuttered the world we live in.

One example of misuse of collected private data is an unauthorised access to it by third parties for malicious purposes, e.g. blackmail. However, if I am a determined and well-funded individual or a company, I can find a way to get almost any info on almost anybody - it's just a matter of price these days...

If we cannot hide, perhaps, we should follow Bob Knight's advice. I.e. get over and used to the fact that we are being tracked 24/7 via all the communication channels, and just carry on with our lives as usual. There are many much more important and lasting things in this life than someone's dirty linen.

In a debate about personal privacy (famous) FAKEGRIMLOCK expressed the same "live with it" point of view as I did above. There was also one person who suggested that my "if you have nothing to hide, you have nothing to fear" argument has been often used by... despots. I bet he clicks on the "I agree" button without reading  the small print of T&Cs which, almost without exception, are full of "despotism".

What is your view on privacy and Big Brother?