Working in IT business I do get involved into discussions about online privacy quite often.
At first I had the opinion that nobody needs to publish private information and hence I could not really see a privacy problem. The rule is simple: Just don't post stuff on the web which you consider to be private.
After my last discussion about this topic I have to revise my opinion a little: There is information about you that you cannot fully control. In former times people were talking about you on the street and spreading the word that way. Nowadays they do it on Facebook. Apart from a probably larger audience, there is no difference. In many cases you cannot control defamation - or even you don't notice. But that is the more problematic part! Whatever you do, people add their own interpretations and speculations. You "share" information most of the time!
Basically your life is not private. It's just a few moments that are really private - where no information is shared. I was about to think about sitting on the toilet - but with two small children even this is an exception. ;-)
With or without your actions, you publish at least a part of yourself (including non-verbal communication). Other people add their interpretations and speculations and maybe tell those to others. In most cases you cannot really do anything about it and simply have to accept.